Transcript A review of quality of service mechanisms in IP

A review of quality of service mechanisms in IP-based
network─integrated and differentiated services,multi-layer
switching,MPLS and traffic engineering
Ray Hunt
Computer Communications 25 (2002) 100-108
Reporter:李儀訢、黃柏維、王皓正
Outline:
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Introduction
Integrated services/RSVP
Differentiated services
Multi-layer switching
Traffic engineering
Conclusions
Introduction
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ISPs are the challenge of offering improved quality of service to
their customer.
NO longer is best effort delivery with no service guarantee
acceptable for many applications.
IP-based networks only provide Best Effort Service , which
implies that there is no guarantee as to delay margins or actual
delivery times.
The IETF has proposed many service models and mechanisms
to meet the demand for QoS.
Include:IntServ/RSVP , DiffServ , MPLS , and Traffic engineering.
Integrated services/RSVP
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The Integrated Services/RSVP (IntServ) model comprises three
classes of service:
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Best effort─ for time delay independent applications
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Guaranteed─ for applications requiring fixed delay
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Predictive─ for applications requiring probabilistic delays
Integrated services/RSVP (cont.)
Differentiated services
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DiffServ has been available in IPv4 by way of the
type of service (TOS).
DS field include: core router , edge router ,
bandwidth broker
Service currently being defined include:
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Assure service ─ for applications requiring better
reliability than best effort service.
Premium service ─ for applications requiring low
delay and low jitter.
DiffServ provides a very different service offering
than IntServ which can be seen from Table1.
Differentiated services (cont.)
Differentiated services (cont.)
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Service and resource allocation using band width management
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There are four main differences:
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IT is the sender that request resources not the receiver
A request can be rejected
A BM can aggregate multiple requests and make a single request to
the next BM
Each domain behaves like a single node represented by the BM.ISP
core routers are not involved in this process.
Differentiated services (cont.)
Multi-layer switching
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Multi-layer switchingare characterised by two components:
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Control and forwarding
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Label swapping
Control and forwarding
Label swapping
Multi-layer switching (cont.)
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Multi-protocol label switching (MPLS)
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The motivation for MPLS is to use a fixed-length label to
decide upon packet handling.
IT is the latest step in the evolution of multi-layer
switching for IP-based network.
Comprise:
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Ingress LSR─ Push Label
Core LSR─ Label Swap
Egress LSR─ Pop Label
Multi-protocol label switching (MPLS)
Traffic engineering
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The traffic engineering is the process of controlling traffic flow
through the network.
Architectural issues of traffic engineering
Traffic engineering (cont.)
Traffic engineering (cont.)
Traffic engineering (cont.)
Conclusions
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Unpredictable performance has been the most significant
problem in the deployment of IP-based network.
IntServ , DiffServ and MPLS are all-important stepping stones in
the evolution of a new IP infrastructure.
Important work has been ─ and continous to be under-taken ─
by the IETF working group.