CIS679: DiffServ Model

Review of Last Lecture 2-bit DiffServ architecture

Review of Last Lecture

Two Planes IntServ DiffServ

Two types of services: relative and absolute Basic mechanism: edge-router, core-router, PHB

2-bit differentiated service

Premium service: (type P) admitted based on peak rate conservative, virtual wire services unused premium goes to best effort

Assured service: (type A) based on expected capacity usage profiles traffic unlikely to be dropped if user maintains

profile. Out-of-profile traffic marked

Traffic Flows

first hoprouter

internalrouter

borderrouter

host

borderrouter

ISP

Company A

Unmarkedpacket flow

Packets in premium andAssured flows have bit set

Leaf Router

Marking at Leaf Router

Forwarding

Metering at Border Router

Leaf router input functionality

ClearA & P

bits

Packetclassifier

Marker 1

Marker N

Forwardingengine

Arrivingpacket Best effort

Flow

1Fl

ow N

Markers: service class, rate, permissible burst size

Marker function in routers

Leaf routers have traffic profiles - they classify packets based on packet header

If no profile present, pass as best effort If profile is for A:

mark in-profile packets with A, forward others unmarked

If profile is for P: delay out-of -profile packets to shape into profile

Markers to implement two different services

Wait fortoken

Set P bitPacketinput

Packetoutput

Test iftoken Set A bit

token

No token

Packetinput

Packetoutput

Drop on overflow

Output forwarding

2 queues: P packets on higher priority queue Lower priority queue implements RED “In or

Out” scheme (RIO) At border routers profile meters test marked

flows: drop P packets out of profile unmark A packets

Router output interface for two-bit architecture

P-bit set?

If A-bit setincr A_cnt

High-priority Q

Low-priority Q

If A-bit setdecr A_cnt

RIO queuemanagement

Packets out

yes

no

RED with In or Out (RIO)

Precursor to Assured Forwarding (AF) PHB Similar to RED, but with two separate

probability curves Has two classes, “In” and “Out” (of profile) “Out” class has lower Minthresh, so packets

are dropped from this class first As avg queue length increases, “in” packets

are dropped

RIO drop probabilities

MaxP

1.0

Minout Minin MaxinMaxout

P(drop)

AvgLen

More drop probability curves (WRED)?

Border router input interface Profile Meters

Arrivingpacket

Is packetmarked?

Tokenavailable?

Tokenavailable?

Clear A-bit

Drop packet

Forwardingengine

A set

P set

token

token

Not marked

no

no

Conclusion

An example of relative DiffServ 2 bit architecture

• Premium service, Assured service Marker at leaf router Output forwarding Meter at border router

Final Review on Part 1

Multimedia basics The four major steps Compression techniques

• Redundancy• Classification

JPEG• DCT

MPEG• Motion prediction • I, B and P frames, GOP• Different units

Final Review on Part 2

Better then best effort services Multimedia requirements to networks TCP

• Window control, Reliability, Flow and congestion control

UDP• Why UDP for multimedia?• TCP friendly• CUDP etc.

Buffer management• Drop-tail, RED and its variations

HTTP and RTP Multicast: address, routing, transport layer and QoS Anycast: network-layer and application layer anycast

Final Review on Part 3

Beyond the best effort services Four Principles Policing Scheduling

• Its relationship with buffer management RSVP

• Receiver driven and soft-state Integrated Service model Differentiated Service model