Delay-based early congestion detection and adaptation in TCP: impact on web performance

  • Authors:
  • Michele C. Weigle;Kevin Jeffay;F. Donelson Smith

  • Affiliations:
  • Department of Computer Science, Clemson University, Clemson, SC 29634, USA;Department of Computer Science, University of North Carolina, Chapel Hill, NC 27599-3175, USA;Department of Computer Science, University of North Carolina, Chapel Hill, NC 27599-3175, USA

  • Venue:
  • Computer Communications
  • Year:
  • 2005

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Abstract

Concerns over the scalability of TCP's end-to-end approach to congestion control and its AIMD congestion adaptation have led to proposals for router-based congestion control, specifically, active queue management (AQM). In this paper we present an end-to-end alternative to AQM-a new congestion detection and reaction mechanism for TCP based on measurements of one-way transit times of TCP segments within a TCP connection. Our design, called Sync-TCP, places timestamps in TCP headers, measures variation in one-way transit times, and uses these measurements as a form of early congestion notification. We demonstrate empirically that: (1) Sync-TCP provides better throughput and HTTP response-time performance than TCP Reno, (2) Sync-TCP provides better early congestion detection and reaction than the Adaptive Random Early Detection with Explicit Congestion Notification AQM mechanism, (3) Sync-TCP's congestion detection and adaptation mechanisms are robust against clock drift, (4) Sync-TCP is an incrementally deployable protocol-Sync-TCP connections can co-exist with TCP Reno connections in a network, and (5) the performance of TCP Reno connections are improved with the addition of even a small percentage of Sync-TCP connections.