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Introduction to
QoS Mechanisms
Instructor Hamid R Rabiee
Spring 2012
Outline
Introduction to QoS
History
QoS Definitions
Basic Functional Blocks of QoS
Call Admission
Resource Reservation
PolicingShaping
Scheduling
Congestion Avoidance Mechanisms
IP Network Architecture
Intserv RSVP
Diffserv MPLS-TE
Summary
2Digital Media Lab - Sharif University of Technology
Introduction ndash Quality of Service (QoS)
The Best Effort Paradigm
Increase in traffic leads to degradation of service for all Some applications are impacted more than
others
Why not just over-provision resources
Everyone can then get the best quality all the timehellip
The QE curve and its implications
Do we need QoS
Users will find new applications that will eventually cause bandwidth to be a limiting factor (Murphyrsquos
Law)
Two main traffic types Delay-sensitive(VOD) Loss-sensitive(Mail)
Relative misuse of available bandwidth by protocols with no throttling mechanism (such as UDP)
over others that do (TCP) may incorrectly penalize conforming flows
Conclusion
We may need QoS mechanisms for guaranteed services across the network
3Digital Media Lab - Sharif University of Technology
QoS ndash Definition(s)
Definition
The end-to-end perspective (We the users) QoS is a quantification of
serviceapplication-relevant measures of network effectiveness against
acceptable levels for measures such as
Delay
Jitter
Loss
response time
throughput
QoS ndash The network architecture perspective (We the providers)
Provide services to specific traffic classes such that QoS can be provided to end-
users on a guaranteeddifferential basis
4Digital Media Lab - Sharif University of Technology
QoS affecting factors
The factors affecting the quality of real time services over packet networks
include
Quantization noise
Bit error ratio
Delay
Contributed by the codec
Contributed by the network
Packet queuing delay caused by queuing packets in the buffer
Propagation delay the time expended for the signal to travel the
transmission distance
5Digital Media Lab - Sharif University of Technology
QoS Affecting Factors
Delay variation or ldquojitterrdquo
Jitter is removed by a buffer in the receiving device
If jitter exceeds the size of the jitter buffersbquo the buffer will overflow and packet
loss will occur
What is the source of delay variation
Packet loss
The choice of codec
Echo control
The design of the network
Blocking probability
6Digital Media Lab - Sharif University of Technology
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Outline
Introduction to QoS
History
QoS Definitions
Basic Functional Blocks of QoS
Call Admission
Resource Reservation
PolicingShaping
Scheduling
Congestion Avoidance Mechanisms
IP Network Architecture
Intserv RSVP
Diffserv MPLS-TE
Summary
2Digital Media Lab - Sharif University of Technology
Introduction ndash Quality of Service (QoS)
The Best Effort Paradigm
Increase in traffic leads to degradation of service for all Some applications are impacted more than
others
Why not just over-provision resources
Everyone can then get the best quality all the timehellip
The QE curve and its implications
Do we need QoS
Users will find new applications that will eventually cause bandwidth to be a limiting factor (Murphyrsquos
Law)
Two main traffic types Delay-sensitive(VOD) Loss-sensitive(Mail)
Relative misuse of available bandwidth by protocols with no throttling mechanism (such as UDP)
over others that do (TCP) may incorrectly penalize conforming flows
Conclusion
We may need QoS mechanisms for guaranteed services across the network
3Digital Media Lab - Sharif University of Technology
QoS ndash Definition(s)
Definition
The end-to-end perspective (We the users) QoS is a quantification of
serviceapplication-relevant measures of network effectiveness against
acceptable levels for measures such as
Delay
Jitter
Loss
response time
throughput
QoS ndash The network architecture perspective (We the providers)
Provide services to specific traffic classes such that QoS can be provided to end-
users on a guaranteeddifferential basis
4Digital Media Lab - Sharif University of Technology
QoS affecting factors
The factors affecting the quality of real time services over packet networks
include
Quantization noise
Bit error ratio
Delay
Contributed by the codec
Contributed by the network
Packet queuing delay caused by queuing packets in the buffer
Propagation delay the time expended for the signal to travel the
transmission distance
5Digital Media Lab - Sharif University of Technology
QoS Affecting Factors
Delay variation or ldquojitterrdquo
Jitter is removed by a buffer in the receiving device
If jitter exceeds the size of the jitter buffersbquo the buffer will overflow and packet
loss will occur
What is the source of delay variation
Packet loss
The choice of codec
Echo control
The design of the network
Blocking probability
6Digital Media Lab - Sharif University of Technology
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Introduction ndash Quality of Service (QoS)
The Best Effort Paradigm
Increase in traffic leads to degradation of service for all Some applications are impacted more than
others
Why not just over-provision resources
Everyone can then get the best quality all the timehellip
The QE curve and its implications
Do we need QoS
Users will find new applications that will eventually cause bandwidth to be a limiting factor (Murphyrsquos
Law)
Two main traffic types Delay-sensitive(VOD) Loss-sensitive(Mail)
Relative misuse of available bandwidth by protocols with no throttling mechanism (such as UDP)
over others that do (TCP) may incorrectly penalize conforming flows
Conclusion
We may need QoS mechanisms for guaranteed services across the network
3Digital Media Lab - Sharif University of Technology
QoS ndash Definition(s)
Definition
The end-to-end perspective (We the users) QoS is a quantification of
serviceapplication-relevant measures of network effectiveness against
acceptable levels for measures such as
Delay
Jitter
Loss
response time
throughput
QoS ndash The network architecture perspective (We the providers)
Provide services to specific traffic classes such that QoS can be provided to end-
users on a guaranteeddifferential basis
4Digital Media Lab - Sharif University of Technology
QoS affecting factors
The factors affecting the quality of real time services over packet networks
include
Quantization noise
Bit error ratio
Delay
Contributed by the codec
Contributed by the network
Packet queuing delay caused by queuing packets in the buffer
Propagation delay the time expended for the signal to travel the
transmission distance
5Digital Media Lab - Sharif University of Technology
QoS Affecting Factors
Delay variation or ldquojitterrdquo
Jitter is removed by a buffer in the receiving device
If jitter exceeds the size of the jitter buffersbquo the buffer will overflow and packet
loss will occur
What is the source of delay variation
Packet loss
The choice of codec
Echo control
The design of the network
Blocking probability
6Digital Media Lab - Sharif University of Technology
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS ndash Definition(s)
Definition
The end-to-end perspective (We the users) QoS is a quantification of
serviceapplication-relevant measures of network effectiveness against
acceptable levels for measures such as
Delay
Jitter
Loss
response time
throughput
QoS ndash The network architecture perspective (We the providers)
Provide services to specific traffic classes such that QoS can be provided to end-
users on a guaranteeddifferential basis
4Digital Media Lab - Sharif University of Technology
QoS affecting factors
The factors affecting the quality of real time services over packet networks
include
Quantization noise
Bit error ratio
Delay
Contributed by the codec
Contributed by the network
Packet queuing delay caused by queuing packets in the buffer
Propagation delay the time expended for the signal to travel the
transmission distance
5Digital Media Lab - Sharif University of Technology
QoS Affecting Factors
Delay variation or ldquojitterrdquo
Jitter is removed by a buffer in the receiving device
If jitter exceeds the size of the jitter buffersbquo the buffer will overflow and packet
loss will occur
What is the source of delay variation
Packet loss
The choice of codec
Echo control
The design of the network
Blocking probability
6Digital Media Lab - Sharif University of Technology
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS affecting factors
The factors affecting the quality of real time services over packet networks
include
Quantization noise
Bit error ratio
Delay
Contributed by the codec
Contributed by the network
Packet queuing delay caused by queuing packets in the buffer
Propagation delay the time expended for the signal to travel the
transmission distance
5Digital Media Lab - Sharif University of Technology
QoS Affecting Factors
Delay variation or ldquojitterrdquo
Jitter is removed by a buffer in the receiving device
If jitter exceeds the size of the jitter buffersbquo the buffer will overflow and packet
loss will occur
What is the source of delay variation
Packet loss
The choice of codec
Echo control
The design of the network
Blocking probability
6Digital Media Lab - Sharif University of Technology
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS Affecting Factors
Delay variation or ldquojitterrdquo
Jitter is removed by a buffer in the receiving device
If jitter exceeds the size of the jitter buffersbquo the buffer will overflow and packet
loss will occur
What is the source of delay variation
Packet loss
The choice of codec
Echo control
The design of the network
Blocking probability
6Digital Media Lab - Sharif University of Technology
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Delay Jitter
7Digital Media Lab - Sharif University of Technology
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
The QoS Perspective
So what is Quality of Service
Ability to provide better service to selected traffic
Distinguish traffic with strict timing requirements
Allocate resources in the network (eg bandwidth buffer priority) so that traffic
gets to destinations quickly and reliably
Do not create bandwidth ndash simply manage it effectively to meet application
requirements
Benefits of using QoS
Dedicated bandwidth
Controlled network latency and jitter
Improved loss characteristics
Control and predictability beyond the ldquobest-effortrdquo concept
8Digital Media Lab - Sharif University of Technology
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS at Different Layers
QoS can be provided at different layers
Application Layer
Transport layer
(system) Network layer
TCP based congestion control scheme is application specific Some
applications can run on UDP some of modified unfriendly TCP for other
user Even more real-time application can not cope the large fluctuation of
Tx Rate due to TCP
Core network does not provide any QoS
To over come this problem network layer QoS is considered
We consider Network layer solutions
9Digital Media Lab - Sharif University of Technology
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Quality of Service Heterogeneity
10Digital Media Lab - Sharif University of Technology
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS11
Principles for QOS Guarantees
Consider a phone application at 1Mbps and an FTP application sharing a
15 Mbps link
bursts of FTP can congest the router and cause audio packets to be dropped
want to give priority to audio over FTP
PRINCIPLE 1 Marking of packets is needed for router to distinguish
between different classes and new router policy to treat packets accordingly
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS12
Principles for QOS Guarantees (more)
Applications misbehave (audio sends packets at a rate higher than 1Mbps assumed
above)
PRINCIPLE 2 provide protection (isolation) for one class from other classes
Require Policing Mechanisms to ensure sources adhere to bandwidth
requirements Marking and Policing need to be done at the edges
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS13
Principles for QOS Guarantees (more)
Alternative to Marking and Policing allocate a set portion of bandwidth to
each application flow can lead to inefficient use of bandwidth if one of the flows
does not use its allocation
PRINCIPLE 3 While providing isolation it is desirable to use
resources as efficiently as possible
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS14
Principles for QOS Guarantees (more)
Cannot support traffic beyond link capacity
Two phone calls each requests 1 Mbps
PRINCIPLE 4 Need a Call Admission Process application flow
declares its needs network may block call if it cannot satisfy the needs
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Basic Functional Blocks of QoS
Call Admission Resource Allocation
SLA (Service Level Agreement)
Advertisement of required bandwidth by user to the network
Provisioning of bandwidth by network for user
Flow Classification
Ability of the network to identify incoming packets (flows) and assign them a pre-defined level of
service
Policing and Shaping
Ability of the network to monitor flows to ensure conformance to advertised traffic characteristics and
provisioned resources
Congestion Avoidance Mechanisms
Ability to monitor buffer utilization levels and regulate flow rates to alleviate congestion on network
links
Scheduling Mechanisms
Queuing mechanisms to provision differing levels of service
15Digital Media Lab - Sharif University of Technology
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Call Admission
Control Plane
Signal the network on type of connection and QoS requirements
Network is responsible for pro-active Bandwidth Management
Establishing the route of the connection
Reserving enough resources to meet QoS requirements
Stochastic reservation
Virtual pipes
Rejecting a call if it does not have enough
resources to meet the call
1048707 Examples
ATM
IntServ (RSVP)
MPLS
16Digital Media Lab - Sharif University of Technology
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Flow Classification
Need a method to identify packetscells in order to provide differential treatment
Examples of Classification Criteria
VC number
MPLS Label
Type of Service
Protocol
Address
Source IP Address
Destination IP Address
Port Number
Source port
Destination port
Incoming interface
DSCP (DiffServ Code Point)
17Digital Media Lab - Sharif University of Technology
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Policing and Shaping
Effect of Policing
Effect of Shaping
18Digital Media Lab - Sharif University of Technology
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Congestion Avoidance
Not congestion management
Monitor traffic loads at egress
network interfaces in order to
anticipate and avoid congestion in
the buffers
Do not accept packet into buffer if
packet fails ldquodiscard testrdquo
Typically works best in tandem with
TCP
Take advantage of TCP retransmission
mechanism by randomly dropping
packets
Reduce chance of tail drop
Minimize chance of global
synchronization
Common schemes
RED (Random Early Detection)
Stochastically drop packets as
congestion begins to increase
WRED (Weighted Random Early
Detection)
Combine stochastic dropping of
packets with IP Precedence
Implemented by two different
algorithms
Average queue size computation
Packet drop probability
19Digital Media Lab - Sharif University of Technology
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Scheduling - Common queueing disciplines
Scheduling algorithms are
important components in the
provision of guaranteed quality
of service parameters such as
delay delay jitter packet loss
rate or throughput
Scheduling Schemes
FIFO (First In First Out)
PQ (Priority Queuing)
WRR (Weighted Round Robin) variants
FQ (Fair Queuing)
Equal weight given to each queue
WFQ (Weighted Fair Queuing)
Variable weight given to each queue
Approximate when packet sizes disparate
Implemented in software
CQ (Custom Queuing)
CBWFQ (Class Based Weighted Fair Queuing)
WFQ where packets are classified into queues
DRR (Deficit Round Robin)
More exact weight given to each queue
20Digital Media Lab - Sharif University of Technology
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Scheduling ndash WFQ Principles
Operational basics
Divide traffic into various queues
Assign a weight (portion of bandwidth) to each queue
Serve each queue according to its weight (in essence desired percentage of
output port bandwidth for the queue)
Each class is ldquoguaranteedrdquo a minimum share of output forwarding capacity
Note that the queues are not in a priority order ndash which means each queue
sees the full server for a fraction of the total time
Allows for configuration of multiple levels of sharing hierarchy
LLQ (Low Latency Queue)
Strict priority queue within CBWFQ paradigm
21Digital Media Lab - Sharif University of Technology
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Putting the Pieces Togetherhellip
Classifier Selects packets based on portions of packet header
Marker MarksRemarks the packet header based on traffic class
Meter Checks compliance to traffic profile and passes result to Marker and ShaperDropper
Shaper Allows for delaying of packets in buffer to enforce compliance with traffic profile
Dropper Drops traffic that does not conform with traffic profile
Congestion Avoidance Checks buffer levels and stochastically drops packets
Scheduler Allows for differential queueing and servicing of packets
22Digital Media Lab - Sharif University of Technology
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Scope of IP QoS
From a TCPIP perspective hellip
23Digital Media Lab - Sharif University of Technology
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
IP Datagram Lifecycle under QoS
24Digital Media Lab - Sharif University of Technology
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
NETWORK ARCHITECTURE
INTSRV AND DIFFSRV
APPROACHES
25Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Integrated Services (Intserv)
Architecture for providing QoS guarantees in IP networks
for individual application sessions
Assumptions
resource must be explicitly managed in order to meet the requirements of
real-time applications
resource reservation routers maintain state info of allocated
resources QoS reqrsquos
26Digital Media Lab - Sharif University of Technology
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Integrated Services (Intserv)
Steps
Application requests its required resource
The network uses a routing protocol to find a path based on the requested
resources
Reservation protocol (RSVP) is used to install the reservation state along
that path
At each hop admission control checks whether sufficient resources are
available to accept the new reservation
After reservation the application can start to send traffic over the path for
which it has exclusive use of the resources
27Digital Media Lab - Sharif University of Technology
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Two services level
guaranteed (delay) service
controlled load service
28Digital Media Lab - Sharif University of Technology
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Service Models
Guaranteed service model
provides deterministic worst case delay bound through strict
admission control and fair queuing scheduling
designed for applications that require absolute guarantees on
delay
controlled load service model
provides a less firm guarantee
a service that is close to a lightly loaded best-effort network
29Digital Media Lab - Sharif University of Technology
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS30
Intserv QoS guarantee scenario
Resource reservation
call setup signaling (RSVP)
traffic QoS declaration
per-element admission control
QoS-sensitive scheduling
(eg WFQ)
request
reply
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Signaling
A flow needs performance guarantee must
declare its QoS requirement
R-spec defines the QoS being requested characterize traffic it will
send into network
T-spec defines traffic characteristics
signaling protocol needed to carry R-spec and T-spec to routers (where
reservation is required)
31Digital Media Lab - Sharif University of Technology
connectionless
(stateless) forwarding
by IP routers
best effort
service
no network
signaling protocols
in initial IP design+ =
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
RSVP Protocol
RSVP (Resource Reservation Protocol) [RFC 2205]
Protocol used for control signals
Transmitting applications use RSVP to describe data traffic characteristics
Receiving applications use RSVP to describe their QoS requirements
Network Elements use RSVP to deliver QoS requests to other network elements
Reservation setup mechanism
Dynamic Applications can dynamically reserve and free network bandwidth
Simplex reservation setup Each side of a connection requiring bandwidth guarantee
must perform a separate reservation procedure
Hop-by-hopreservation style Every RSVP-aware hop benefits from the RSVP messages
traversing a flow ndash end-to-end guarantee not possible if some intermediate elements do
not support RSVP
Different reservation styles for unicast and multicast traffic
32Digital Media Lab - Sharif University of Technology
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking33
RSVP Design Goals
Accommodate heterogeneous receivers (different bandwidth along paths)
Accommodate different applications with different resource requirements
Make multicast a first class service with adaptation to multicast group membership
Leverage existing multicastunicast routing with adaptation to changes in underlying unicast multicast routes
Control protocol overhead to grow (at worst) linear in receivers
Modular design for heterogeneous underlying technologies
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking34
RSVP does nothellip
bull specify how resources are to be reserved
bull rather a mechanism for communicating needs
bull determine routes packets will take
bull thatrsquos the job of routing protocols
bull signaling decoupled from routing
bull interact with forwarding of packets
bull separation of control (signaling) and data (forwarding)
planes
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking35
RSVP overview of operation
senders receiver join a multicast group
done outside of RSVP
senders need not join group
sender-to-network signaling
path message make sender presence known to routers
path teardown delete senderrsquos path state from routers
receiver-to-network signaling
reservation message reserve resources from sender(s) to receiver
reservation teardown remove receiver reservations
network-to-end-system signaling
path error
reservation error
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
RSVP Usage Options
36Digital Media Lab - Sharif University of Technology
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking37
RSVP simple audio conference
H1 H2 H3 H4 H5 both senders and receivers
multicast group m1
no filtering packets from any sender forwarded
audio rate b
only one multicast routing tree possible
H2
H5
H3
H4
H1
R1 R2 R3
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking38
in
outin
out
in
out
RSVP building up path state
H1 hellip H5 all send path messages on m1
(address=m1 Tspec=b filter-spec=no-filterrefresh=100)
Suppose H1 sends first path message
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4m1
m1
m1
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking39
in
outin
out
in
out
RSVP building up path state
next H5 sends path message creating more state in routers
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
m1
m1
m1
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking40
in
outin
out
in
out
RSVP building up path state
H2 H3 H5 send path msgs completing path state tables
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L5 L7
L6
L1
L2 L6 L3L7
L4
L5
L6
L1
L6
L7
L4L3L7
L2m1
m1
m1
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking41
RSVP receiver reservation example 1
H1 wants to receive audio from all other senders
H1 reservation msg flows uptree to sources
H1 only reserves enough bandwidth for 1 audio stream
reservation is of type ldquono filterrdquo ndash any sender can use reserved bandwidth
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking42
in
out
RSVP receiver reservation example 1
H1 reservation msgs flows uptree to sources
routers hosts reserve bandwidth b needed on downstream links towards
H1
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
m1
m1
m1
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking43
in
out
RSVP receiver reservation example 1 (more)
next H2 makes no-filter reservation for bandwidth b
H2 forwards to R1 R1 forwards to H1 and R2 ()
R2 takes no action since b already reserved on L6
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
7 Multimedia Networking44
in
out
RSVP receiver reservation issues
What if multiple senders (eg H3 H4 H5) over link (eg L6)
arbitrary interleaving of packets
L6 flow policed by leaky bucket if H3+H4+H5 sending rate exceeds b
packet loss will occur
H2
H5
H3
H4
H1
R1 R2 R3L1
L2 L3
L4
L5
L6 L7
L1L2 L6
L6
L1(b)
in
out
L5L6 L7
L7
L5 (b)L6
in
out
L3L4 L7
L7
L3 (b)L4L2
b
bb
b
b
b
b
b
b
(b)m1
m1
m1
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Integrated Services (Intserv)
Disadvantage
Applicable to long lasting traffic (video conferencing)
Scalability problem
may not be able to cope with a very large number of flows at high speeds
requires the support of accounting and settlement between different service
providers
Flexible Service Models
Intserv has only two classes Also want ldquoqualitativerdquo service classes
Potential Application Area
IP telephony video conferencing over corporate intranets
45Digital Media Lab - Sharif University of Technology
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Differentiated Services (DiffServ)
Uses a combination of edge policing provisioning and traffic
prioritization to achieve service differentiation
Resource allocation to aggregated traffic rather than individual flows
Traffic policing on the edge and class-based forwarding in the core
Diffserv approach
simple functions in network core relatively complex functions at edge routers
(or hosts)
Donrsquot define service classes provide functional components to build service
classes
46Digital Media Lab - Sharif University of Technology
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Diffserv Architecture
Edge router
- per-flow traffic management
- marks packets as in-profile and
out-profile
Core router
- per class traffic management
- buffering and scheduling
based on marking at edge
- preference given to in-profile
packets
- Assured Forwarding
scheduling
r
b
marking
47Digital Media Lab - Sharif University of Technology
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
DiffServ Components
At the edge of DiffServ domain
Classification and Marking
PolicingShaping
Within the core of the DiffServ domain
Congestion Avoidance
Scheduling
Combination of LLQ CBWFQ for differential treatment to DiffServ Classes (Why do we
need LLQ)
Result
Provide differential treatment to Behavior Aggregates (BA) by proper configuration
Remove complexity from core of network and place it at edges
48Digital Media Lab - Sharif University of Technology
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Router Functionality
Network edge routers
Packet classification service level agreement (SLA) and traffic
type
Responsible for mapping packets to their appropriate forwarding
classes per-hop behavior (PHB) Each PHB is represented by a 6
bit DSCP (differential service code point)
Set DSCP in packet header DS field modified TOS field
Nonconforming traffic may be dropped delayed or marked with a
different forwarding class
Interior (core) routers
traffic classification and forwarding use DSCP as index into forwarding table
49Digital Media Lab - Sharif University of Technology
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Router Functionality
Classifier MarkerShaperDropper
Meter
Traffic conditioning
Network edge routers
traffic conditioning (policing marking dropping) SLA negotiation
PHB group
data
PHB class
real-time
PHB class
PHB 11
PHB 22
PHB 21
low delay
highimportance
high delay
lowimportance
50Digital Media Lab - Sharif University of Technology
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Edge-router Packet Marking
bull class-based marking packets of different classes marked differently
bull intra-class marking conforming portion of flow marked differently than non-
conforming one
profile pre-negotiated rate A bucket size B
packet marking at edge based on per-flow profile
Possible usage of marking
User packets
Rate A
B
51Digital Media Lab - Sharif University of Technology
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Classification and Conditioning
Packet is marked in the Type of Service (TOS) in IPv4 and Traffic
Class in IPv6
6 bits used for Differentiated Service Code Point (DSCP) and
determine PHB that the packet will receive
2 bits are currently unused
52Digital Media Lab - Sharif University of Technology
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Classification and Conditioning
may be desirable to limit traffic injection rate of some class
user declares traffic profile (eg rate burst size)
traffic metered shaped if non-conforming
53Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Forwarding (PHB)
PHB result in a different observable (measurable) forwarding
performance behavior
PHB does not specify what mechanisms to use to ensure required PHB
performance behavior
Examples
Class A gets x of outgoing link bandwidth over time intervals of a specified
length
Class A packets leave first before packets from class B
54Digital Media Lab - Sharif University of Technology
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Forwarding (PHB)
PHBs being developed
Expedited Forwarding pkt departure rate of a class equals or exceeds
specified rate
logical link with a minimum guaranteed rate
Assured Forwarding 4 classes of traffic
each guaranteed minimum amount of bandwidth
each with three drop preference partitions
55Digital Media Lab - Sharif University of Technology
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Diffserv and MPLS
Both are WAN QoS mechanisms While Diffserv is used for traffic
aggregation and provisioning of differentiated services MPLS is
mainly used for traffic aggregation and load balancing
56Digital Media Lab - Sharif University of Technology
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
MPLS ndash Traffic Engineering
Traffic Engineering is all about placing traffic where there is bandwidth
Optimize network resources through careful distribution of traffic in network
Provide ability to arbitrarily segregate flows at any desired level of granularity
and route those flows independently from one another
Constraint Based Routing (CBR)
Allow TE Cost Metric to be based on parameters such as
Hop Count
Delay
Available Bandwidth
TE Cost
57Digital Media Lab - Sharif University of Technology
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Multiple Protocol Label Switching (MPLS)
Multiple Protocol Label Switching (MPLS) facilitates the marriage of IP
to OSI Layer 2 technologies
Originally introduced as a WAN mechanism for forwarding packets using
label switching instead of the IP address-based routing and provide
differentiated QoS
It has found its most use in Traffic Engineering (TE)
TE requires that traffic follows specific possibly nonoptimal routes to enable
diverse routing traffic load balancing and other means of optimizing network
resources
MPLS forces traffic into these routes or Label Switched Paths (LSPs)
58Digital Media Lab - Sharif University of Technology
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
MPLS ndash Basics
Label Switching
Originally designed to make routers faster
Longest prefix lookup vs fixed label lookup
Separates control and data plane
Higher forwarding rates
Enables traffic engineering
Scalable high-performance IP networks
Multi-Protocol
ldquoLabelrdquo as universal identifier
Single device can transport data units of multiple protocols
Eg IP datagrams and ATM cells through an ATM switch
59Digital Media Lab - Sharif University of Technology
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
MPLS
Main advantages of MPLS
Support Traffic Engineering (TE) which is used essentially to control traffic
flow
Support VPN (Virtual Private Network)
Both TE and VPN help delivery of QoS for multimedia data
60Digital Media Lab - Sharif University of Technology
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
MPLS ndash TE Operation
Optimize route selection of LSP based on TE metric
Off-Line Mode
Compute routes periodically (using CBR) and switch to new routes during maintenance periods
Could lead to operational delays as all routes (even existing demands) are re-established
On-Line Mode
Route computation performed incrementally with arrival of each new demand
Does not require rerouting of existing traffic
Inefficient optimization as compared to Off-Line Mode
Two modes can be combined at different time scales
61Digital Media Lab - Sharif University of Technology
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
DiffServ-Aware MPLS-TE
Combine TE concept of routing with service provisioning concept of DiffServ
CBR
New concept of sub pools (within the global available bandwidth pool)
Allows for a more restrictive bandwidth constraint that can be used by LSPs meant for ldquoguaranteedrdquo traffic
Allow LSPs to request bandwidth from a specific sub pool
Concept of ensuring QoS for flows
Forward Equivalence Class (FEC)
A set of classification rules to allow classification of packets
Examples IP Prefix Egress Router Application flow
Use Marking functionality to map FEC onto MPLS header
E-LSP
EXP bits on MPLS header are used to carry information about FEC
L-LSP
MPLS Label contains information about FECs
Map EXP classes to DiffServ PHB for specific scheduling policies
62Digital Media Lab - Sharif University of Technology
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Routers or LSRs
In the MPLS network routers are called label switching routers
(LSR)
Edge LSRs (also called LERs) provide the interface between the external IP
network and the LSP
Core LSRs provide transit services through the MPLS cloud using the pre-
established LSP
In a SP network on the ingress the Edge LSR accepts IP packets and
appends MPLS labels
On the egress an edge LSR terminates the LSP by removing MPLS labels
and resorting to the normal IP forwarding
63Digital Media Lab - Sharif University of Technology
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Summary - IP QoS Framework
64Digital Media Lab - Sharif University of Technology
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS65
IntServ vs DiffServ
IntServ network DiffServ
network
Call blocking approach Prioritization approach
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS66
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Granularity of service
differentiation
Individual Flow Aggregate of
flows
State in routers(eg
scheduling buffer
management)
Per Flow Per Aggregate
Traffic Classification
Basis
Several header fields DS Field
Type of service
differentiation
Deterministic or
statistical guarantees
Absolute or
relative
assurance
Admission Control Required Required for
absolute
differentiation
Signaling Protocol Required(RSVP) Not required for
relative schemes
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
QoS67
Comparison of Intserv amp Diffserv Architectures
Intserv Diffserv Coordination for
service differentiation
End-to-End Local (Per-Hop)
Scope of Service
Differentiation
A Unicast or Multicast
path
Anywhere in a
Network or in
specific paths
Scalabilty Limited by the number
of flows
Limited by the
number of classes
of service
Network Accounting Based on flow
characteristics and QoS
requirement
Based on class
usage
Network Management Similar to Circuit
Switching networks
Similar to existing
IP networks
Interdomain
deployment
Multilateral
Agreements
Bilateral
Agreements
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Common Acronyms
68Digital Media Lab - Sharif University of Technology
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
References
ldquoQuality of Service Control in High-speed Networksrdquo by HJ Chao X Guo John Wiley and Sons
2002
QoS
Y Bernet ldquoNetworking Quality of Service and Windows Operating Systemsrdquo New Riders Publishing 2001
ISBN 1-57870-206-2
Z Wang ldquoInternet QoS ndash Architectures and Mechanisms for Quality of Servicerdquo Morgan Kaufmann
Publishers 2001 ISBN 1-55860-608-4
httpwwwciscocom
httpwwwqosforumcom
Protocol Standards (httpwwwietforghomehtml)
IntServ
RFC 2208 2209 2210 2211 2212 2215 2216 2750 2998 3006
DiffServ
RFC 3140 3168 3260 3246 3270 3289
MPLS
RFC 3031 3032 3034 3035
MPLS httpwwwmplsrccom
69Digital Media Lab - Sharif University of Technology
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70
Digital Media Lab - Sharif University of Technology
Next Session
Call Admission Control
70