Easing Congestion in Computer Networks using the Receiver-Window Modification (RWM) Scheme

Abstract

Random Early Detection (RED), Adaptive RED (ARED), BLUE and other Active Queue Management (AQM) queues have been proposed to replace drop-tail queues for Transmission Control Protocol/Internet Protocol (TCP/IP) networks to ease network congestion. Together with the Exp licit Congestion Notification (ECN) scheme, they had shown some pro mise over the drop tail queues. However, the timeout mechanism or the duration of the reception of three duplicate acknowledgements (ACKs), due to early-dropped packets, delays the response time of TCP in reducing the network congestion. Moreover, using ECN has its downsides: i) its messages may get lost; and ii) TCP implementations at the source, router and the destination have to be ECN-co mpliant (which presents a significant problem in today's implementations). To minimize these problems, this paper presents a novel AQM modification scheme called Receiver-W indow Modification (RWM), wh ich can be used together with any AQM queue for congestion avoidance in packet switched networks, especially at ingress and gateway routers. RWM improves on the average queue sizes, one-way end-to-end packet delays, delay jitter, throughput and number of dropped packets. It also overcomes the dependency of these AQM queues on the queues of downstream routers since ECN messages may get dropped or delayed due to congestion at these routers. We carry out extensive NS2 simulat ions to show our results and to support our claims.