TCP: Improving Startup Dynamics by Adaptive Timers and Congestion Control

Abstract

This paper studies the startup dynamics of TCP on both high as well as low bandwidth-delay network paths and proposes a set of enhancements that improve both the latency as well as throughput of relatively short TCP transfers. Numerous studies have shown that the timer and congestion control mechanisms in TCP can have a limiting effect on performance in the startup phase. Based on the results of our study, we propose mechanisms for adaptingTCP in order to yield increased performance. First, we propose a framework for the management of timing in TCP. Second, we show how TCP can utilize the proposed timer framework to reduce the overly conservative delay associated with a retransmission timeout. Third, we propose the use of packet pacing in the initial slow-start to improve the performance of relatively short transfers that characterize the web traffic. Finally, we quantify the importance of estimating the initial slow-start threshold in TCP, specially on high bandwidth-delay paths.