Supporting differentiated services using ATM ABR service

A general framework and architecture called differentiated services (Diffserv) has been proposed by the IETF to support service differentiation among different IP flows traversing a network. The key idea in Diffserv is to achieve scalability through handling aggregates of traffic instead of individual flows. More specifically, at the ingress edge router, each flow is shaped and classified into one of few service classes. Based on these service classes, packets are then forwarded and discarded (if necessary) with different priorities in network core routers/switches. As many network service providers today employ ATM in their backbone networks, there is tremendous interest in supporting IP Diffserv in an ATM environment. This paper presents a study on using ATM ABR service to support IP Diffserv. The idea is to use the flow control mechanism in ABR to eliminate the need for discarding packets inside the ATM network, while service differentiation among different IP flows can simply be supported by proper packet scheduling and/or discarding mechanisms at the ingress edge routers/switches. Scalability is achieved by setting up an ABR virtual circuit (VC) between each pair of ingress and egress routers rather than on a per-flow basis. A simulation study of this Diffserv framework over ATM using the Opnet simulation tool is presented to validate our idea