Delivering End-to-End Statistical QoS Guarantees for Expedited Forwarding

摘要

This paper presents an admission control framework for EF traffic in a Differentiated Service network. The aim is to overcome the limitations, in terms of achievable efficiency, which are proper of a deterministic "worst-case" approach based on the-zero loss assumption. An admission control procedure is defined which provides quantifiable end-to-end QoS 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 approach 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 conflicts at burst scale in the queue, and allows for simple analytical handling of the per-flow loss process. The degradation of the statistical characteristics of the flow along its path are taken into account. Finally, a comparison between analytical bounds and actual performance results obtained by simulations is presented. The results show that the requested QoS targets are largely met and that the achievable efficiency is much higher than that derived from worst case allocation.