A review of quality of service mechanisms in IP-based network─integrated and differentiated services,multi-layer switching,MPLS and traffic engineering

Ray HuntComputer Communications 25 (2002) 100-108

Reporter: 李儀訢、黃柏維、王皓正

Outline: Introduction Integrated services/RSVP Differentiated services Multi-layer switching Traffic engineering Conclusions

Introduction 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 The Integrated Services/RSVP (IntServ) model comprises three classes of service:

Best effort─ for time delay independent applications Guaranteed─ for applications requiring fixed delay Predictive─ for applications requiring probabilistic delays

Integrated services/RSVP (cont.)

Differentiated services 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:

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.) Service and resource allocation using band width

management

There are four main differences: 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 Multi-layer switchingare characterised by two components:

Control and forwarding Label swapping

Control and forwarding

Label swapping

Multi-layer switching (cont.) Multi-protocol label switching (MPLS)

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: Ingress LSR─ Push Label Core LSR─ Label Swap Egress LSR─ Pop Label

Multi-protocol label switching (MPLS)

Traffic engineering 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 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.