Performance Modeling of Differential Fair Buffer Allocation

The Guaranteed Frame Rate (GFR) service is viewed as the most promising ATM service for carrying aggregate TCP/IP traffic over large distances. In this work, we develop an analytical model to assess the performance of TCP over the Differential Fair Buffer Allocation implementation suggested by the ATM Forum. We consider the problem of a single GFR VC fed by multiple TCP Reno sources. The proposed model distinguishes itself from prior work in two The first author of this work was supported in part by the “Comissionat per a Universitats i Recerca” of the “Generalitat de Catalunya” under Project 1999SGR00126 and the Deutscher Akademischer Austauschdienst through the Technical University Hamburg-Harburg. Corresponding Author. Current Mailing Address: Institut für Neuroinformatik, ETHZ/UNIZH, Winterthurerstr. 190, Haus 55, 8057 Zurich, Switzerland. E-mail: [email protected] ways: it captures the behavior of aggregate TCP traffic and it explicitly allows for queue analysis. From a modeling point of view, our study shows that the reactive behavior of TCP in congestion avoidance can be approximated by a two-node Markov chain. In terms of performance measures, we quantify the impact of traffic aggregation on queueing performance. Among many other results, our model predicts that, although the mean queue length seems to reach a maximum at a certain aggregation level, the mean loss probability appears to increase linearly with the number of sources.