TCP-friendly traffic conditioning in DiffServ networks: A memory-based approach

Abstract

Recently, there has been a considerable research interest in designing intelligent markers, tailored for TCP traffic. Markers, one of the building blocks of a traffic conditioner play a major role for resource allocation in a Differentiated Services (DiffServ) network. The TCP dynamics make the design of a marker difficult in many respects. In this paper, we list out the issues related to designing a TCP-friendly marker and propose an intelligent two-colour marker, namely, memory-based marker (MBM) to address those issues. We then extend this concept for a three-colour marker, memory-based three-colour marker (MBTCM), to be deployed for the assured forwarding per-hop behaviour in a DiffServ network. We illustrate the benefits of the MBTCM over time sliding window three-colour marker. The markers were implemented in NS simulator and extensive simulations were done to study their behaviours. Our results show significant improvement in TCP performance, especially in achieving fairness among priority flows with distinct round trip times, windows, and target rates. The markers are capable of protecting TCP flows in cases of congestion caused by the unruly UDP flows. We also investigate the impact of coexisting assured service UDP flows on the assurance to the TCP flows. The major benefits of our markers are its simplicity, least sensitivity to parameters and transparency to the end hosts. © 2002 Elsevier Science B.V. All rights reserved.