2010. Március 22.

Internet QoS: Pieces of the puzzle

• Introduction

• Definitions and Terminology

• Internet Service Regulation

• QoS Architectural Issues

• Conclusions: Joining the Pieces Together

Topics:

2

•  Internet QoS: Pieces of the Puzzle:

IEEE Comm. Magazine, 2010. 01. p. 86-94

• QoS:

http://en.wikipedia.org/wiki/Quality_of_service

• What is QoS?

http://www.tomahawkcomputers.com/qo

s.html

• QoS Components:

http://www.ciscopress.com/articles/articl

e.asp?p=352991&seqNum=4

Sources:

3

Introduction

• Quality of Service

• resource reservation control mechanisms

• ability to provide different priority to

different applications

• guarantees a certain level of performance

to a data flow, eg: real-time streaming

• important if the network capacity is

insufficient

What is QoS?

5

The Internet is

• unregulated

• connectionless

• designed without QoS!

• Routers and switches cannot provide QoS

cheap, fast

• Best effort: default QoS level

Problem:

6

• IP QoS is not Internet QoS

• needed:– more architectures

– scalability

• IP was designed without QoS– Big growth rate

– Driven by market demands

– Many autonomous systems

• needed:– simple

– pragmatic

Why QoS is not widely used? (1):

7

• No consensus on the exact meaning of Internet

service

• needed:– Understand the benefits of QoS

– Good business models including QoS

• Free mentality and internet neutrality– Investment in QoS cost for the end-users

• needed:– flexible

– rigid

Why QoS is not widely used? (2):

8

Definitions and Terminology

• Packet loss

• Latency: end-to-end delay

• Jitter: delay variation

• Uptime: availability

• Throughput: data trasfer rate

QoS parameters:

10

parameter voice service average Internet maximum

Internet

Packet loss 1% 2% 27%

Latency 200 ms 65 ms 85 ms

Jitter 30 ms - -

IntServ:

• Reserving network resources

• RSVP protocol

• Not scalable, not supported

DiffServ:

• Marked packets by type

• Queuing strategies in routers and switches

• Not widely used: „the costs of premium are too high relative

to the perceived benefits”

BE (= Best Effort):

• Not really QoS, just FIFO queuing strategy

QoS categories, mechanisms:

11

CoS (= Class of Service):

12

• Applying a set of priority

levels

• Implementation: – IntServ

– DiffServ:

PHB (= Per Hop Behavior):

a service class

• EF (= Expedicted Forwarding)

• AF (= Assured Forwarding)

• BE (= Best Effort)

• Business oriented

• Technical specifications:

– SLS (= Service Level Specification):

guideline for impelentation

– SLO (= Service Level Objetive): subset of

SLS, describes the goals

• Main drivers: voice and video applications

• Eg:– MOS = Mean Opinion Score

– ASR = Answer Seizure Ratio, percentage of calls

that are successfully completed

– Guaranteed uptime

SLA (= Service Level Agreement):

13

• Only local agreement

• Not rigorous

• Presented as terms of service

– without CoS

– Limits the responsibility of ISPs

– Little assurance of service quality

Problems with SLA:

14

• 98% of

– E-mail response time does not exceed 20 s

– Connenction to hosted server does not exceed 1,5 s

– Website download does not exceed 8 s

Problems with SLA – example:

15

• Subsription-based QoS:

– Fixed bandwidth allocated

– Pay for the service

– Unused

• On-demand QoS:

– According to actual needs allocated

– Pay-per-use

– No guarentee

Types of QoS(1):

16

• Soft QoS:– No service quality assured during abnormal network

conditions

– Not good for applications that need predictable service

quality

– Not attractive enough to pay

– Not much better as Best Effort

• Hard QoS:– Provides predictable service quality

– Attractive enough to pay extra fee

– Difficult for ISPs to provide QoS under abnormal network

conditions

Types of QoS(2):

17

• Explicit QoS:

– The customer explicitly requires a specific

service level

– selling QoS as an option

• Implicit QoS:

– The customer does not specifically

asks for QoS

– Embedded into services, eg: premium service

– No special fee

Types of QoS(3):

18

• TE (= Traffic Engineering):– Performance evaluation– Optimization of networks

• TM (= Traffic Management):– Network operation

• TC (= Traffic Control):– Means and actions

• Usage:– By vendors to implement CoS– By ISPs to offer differenciated services– By Internet backbone providers to achieve

specific network performance– By IT departments to prioritize traffic

Other issues:

19

QoS planning:To be considered together:

• Topology

• Capacity

• Traffic

• Routing methods

• Control schemes

Aim:

• To optimize network performance

• To be QoS not a constraint, but an objective20

Reliability:

• For customers:

• Availability of end-to-end functionality

• For the network provider:

• Ability to experience failures

• No impact into the service

21

Internet Service Regulation

Regulation(1):

• Internet service:

– Regulate the Internet as a whole service

– Regulate specific services

• Eg: Internet telephony

– ILECs (= Incumbent Local Exchange

Carriers):

basic service

– ISPs: embedded service23

Regulation(2):

• Common standard:– Difficult

– Sophisticated

– Costly OAM (= Operation, Administration and

Maintenance)

• Regulators:– Rather penalties, than incentives

– Minimum targets

• Responsibility:– Service is sold by ISPs and delivered over the ILEC

infrastructure

– Difficult to specify responsibility 24

Internet neutrality vs Two-tier Internet

• Internet neutrality: – Users control the content they view

– good for data applications

– New definition: equal treatment among similar

applications

• Two-tier Internet:– ISPs discriminate content according to payment

– Good for delay-sensitive applications, eg: voice, video

– Sophisticated

• Hot debate! 25

Service monitoring and accounting

• Monitoring:– Initiated by the operator

– Obtains a general view of

the network performance

• Accounting:– Requested by the customer

– Sophisticated

• Can use the same collection

tools 26

Internet Service Monitoring:• ISPs use self-reporting systems

• Regulators can audit the ISP logs

• RAQMON (= Real-time Applications QoS Monitoring

Framework): to improve service quality

• Internet traffic reports:– Internettrafficreport.com

– www-iepm.slac.stanford.edu

– Uses ping

– Measures packet loss and delay

– USA and developed / developing countries

– 37% of the world has poor packet loss ratio

27

Internet Traffic report:

28

Internet Service Accounting:

• No standard model

• 1991: accounting framework (made by OSI)

• Motivations, pros:– Provides feedback for the user

– Verifies performance

– Penalizes inefficient / reward efficient usage

• Cons: – overhead

– Detailed information about the user protection

– Complex OAM, high costs 29

Internet Service Pricing:• Key role for success

• Flat pricing:– Simple

– No overhead

– Low management costs

but:

– Over consuming

– Inefficient in congestion

situations

• Trade-off:– ISPs want predictable incomes

– Users want flexible pricing and

not paying for unused services30

Internet Service Marketing:

Management process

Identifies customers

requirements

Last step: advertising

Trade-off: „how to meet

customer requirements

and satisfy in a

profitable manner”31

A feasible business model:

Presenting value added services with the

Internet service

Embedded services, eg: video conference,

IPTV

Pricing relies on usage growth

„service providers should price QoS into their

services and not sell QoS explicitly”32

QoS Architectural Issues

Issues:

QoS supported at

application, transport,

network, data link layer

Some of them

Where, when ,how to

perform QoS routing and

signaling?34

DiffServ (= Differentiated Services):• Scalable

• Efficient for streaming, file transfer

• Inefficient for delay-sensitive applications

• Factors:– Cost of deployment

– Impact on performance

– Complexity of provisioning

– Impact on network planning and monitoring

• Best performance: premium traffic is a minor

proportion of overall traffic35

Application level QoS: Applications adjust service level

Requires a signaling protocol, eg: RSVP

Requires IntServ or DiffServ

Problems:

– Scalability (IntServ)

– No means for negotiating the service level (DffServ)

Solution: hybrid model, but not yet demonstrated

36

Transport Layer QoS: Compatible with DiffServe

No need to involve the application

Problem: a QoS level provided which is not needed or not enough

TCP:

– Flow and congestion control: slow start, windowing

– Error control: retransmission, ACK mechanism

– Not adequate for delay-sensitive applications

UDP:

– No delivery guarantees

– Requires higher level protocol, eg: RTP

– Adequate for delay-sensitive applications37

QoS Routing(1): Assumption: BE (= Best Effort) path is used for

BE and distinguished traffic No path discovery feature routing protocol

needed Already existing:

– QOSPF (= Quality Of Service Path First)

– Q-BGP (= QoS-Enhanced Border Gateway Protocol) Problem: critical issues not addressed, eg:

processing delay, convergence time, instability, inaccuracy 38

Solution:

– scalability: SLA based on the local QoS capabilities

– Single-domain QoS

– Multidomain QoS

– The whole Internet

– Q-BGP (= QoS-Enhanced Border Gateway Protocol)

– Application-layer QoS routing

– Performance-based routing: best routes selected by

monitoring the network performance

– Multiple connections to other ISPs

– AQR (= Assured Quality Routing): dynamically reroutes

traffic

QoS Routing(2):

39

IP over QoS-driven lower layer technologies Transport technologies, eg:

– Ethernet

– OBS (= Optical Burst Switching)

Traffic classification

40

A viable QoS Architecture Layer 7 switching: processing of layer 2 up

to layer7 header Web switch: can interpret HTML tags and make

decisions at layer 2 or 3 Load balancing

Web caching Move content close to the end user

Popular, good results

41

Conclusion: Joining the Pieces

Together

Conclusion:• Customer’s willingness to pay depend on the effectiveness of

the model

• ISP: sell QoS implicitly without special fees

• Adequate trade-off between penalties and incentives

• Goal of QoS: improve overall Internet performance

• QoS should rely on usage growth

• Selling service bundles: Best Effort should be only one bundle

• Not necessarily CoS

• Only effective when a small fraction of the traffic has to be

prioritized

• Planning, TE, OAM, accounting, reliability play key roles43

The puzzle:

44

• Introduction

• Definitions and Terminology

• Internet Service Regulation

• QoS Architectural Issues

• Conclusions: Joining the Pieces Together

Internet QoS: Pieces of the Puzzle

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