Delivering end-to-end statistical QoS guarantees for expedited forwarding

This paper presents an admission control framework for Expedited Forwarding (EF) traffic in a Differentiated Service Network The aim is to overcome th e limitations, in terms of achievable efficiency, which are proper of a det erministic "worst-case" approach based on the zero-loss assumption. An admi ssion control procedure is defined which provides quantifiable end-to-end Q oS guarantees in terms of maximum delay and per-flow loss probability. The admission control scheme relies on the analytical derivation of a bound for the per-flow loss probability at a generic network node. The analytical ap proach is based on the insertion of a discarding device before the EF queue . The purpose of the dropper is to discard packets in order to avoid confli cts at burst scale in the queue, and allows for simple analytical handling of the per-how loss process. The degradation of the statistical characteris tics of the flow along its path are taken into account. Finally, a comparison between analytical bounds and actual performance resu lts obtained by simulations is presented. The results show that the request ed QoS targets are largely met and that the achievable efficiency is much h igher than that derived from the worst-case allocation. (C) 2001 Elsevier S cience B.V. All rights reserved.