On mapping of QoS between integrated services and differentiated services

Abstract

End-to-end QoS in IP networks views Intserv, acting on a per-flow basis, at the peripheries of large core networks where Diffserv, acting on aggregation of flows, operates. In this context, it is necessary to map QoS, in terms of QoS parameters, between the individual and the aggregate flow levels. This is crucial as only the individual, Intserv flow performance is relevant to the end user, whereas the aggregate, Diffserv view is of interest to the network operator only. A deterministic approach at the packet level reveals the presence of synchronization that may result in biases of loss and delay among the individual flows at a Diffserv router, and at the edge router where packets are tagged according to their conformance. We show that, qualitatively, packet loss at the Diffserv level results in 'bursty loss' at the Intserv level. Quantitatively, packet loss at the Diffserv region is first related to consecutive, Intserv packet loss and then to the local packet loss at the Intserv level. As for delay, synchronization may lead a packet to experience maximum delay at every network element of the end-to-end path.