Why did IntServ fail

Differentiated Services (Diffserv)

Diffserv Architecture

Cs 552 Computer Networks Quality Of Service

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Recap of RSVP

PATH message

sender template and traffic spec
advertisement
mark route for RESV message
follow data path

RESV message

reservation request, including flow and filter spec
reservation style and merging rules
follow reverse data path

Other messages

PathTear, ResvTear, PathErr, ResvErr

Why did IntServ fail?

Economic factors

Deployment cost vs Benefit

Is reservation, the right approach?

Multicast centric view

Is per-flow state maintenance an issue?
More about QoS in general …

What is the Problem?

Goal: provide support for wide variety of applications:

Interactive TV, IP telephony, on-line gamming (distributed simulations), VPNs, etc

Problem:

Best-effort cannot do it?
Intserv can support all these applications, but

Too complex
Not scalable

Differentiated Services (Diffserv)

Build around the concept of domain
Domain – a contiguous region of network under the same administrative ownership
Differentiate between edge and core routers
Edge routers

Perform per aggregate shaping or policing
Mark packets with a small number of bits; each bit encoding represents a class (subclass)

Core routers

Process packets based on packet marking

Far more scalable than Intserv, but provides weaker services

Diffserv Architecture

Ingress routers

Police/shape traffic
Set Differentiated Service Code Point (DSCP) in Diffserv (DS) field

Core routers

Implement Per Hop Behavior (PHB) for each DSCP
Process packets based on DSCP

Ingress

Egress

Ingress

Egress

DS-1

DS-2

Edge router

Core router

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Cs 552 Computer Networks Quality Of Service

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