Linear stability of TCP/RED and a scalable control

  • Authors:

  • Steven H. Low;Fernando Paganini;Jiantao Wang;John C. Doyle

  • Affiliations:

  • Department of Engineering and Applied Science, California Institute of Technology, Pasadena, CA;Department of Electrical Engineering, University of California, Los Angeles, CA;Department of Engineering and Applied Science, California Institute of Technology, Pasadena, CA;Department of Engineering and Applied Science, California Institute of Technology, Pasadena, CA

  • Venue:
  • Computer Networks: The International Journal of Computer and Telecommunications Networking
  • Year:
  • 2003

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Abstract

We demonstrate that the dynamic behavior of queue and average window is determined predominantly by the stability of TCP/RED, not by AIMD probing nor noise traffic. We develop a general multi-link multi-source model for TCP/RED and derive a local stability condition in the case of a single link with heterogeneous sources. We validate our model with simulations and illustrate the stability region of TCP/RED. These results suggest that TCP/RED becomes unstable when delay increases, or more strikingly, when link capacity increases. The analysis illustrates the difficulty of setting RED parameters to stabilize TCP: they can be tuned to improve stability, but only at the cost of large queues even when they are dynamically adjusted. Finally, we present a simple distributed congestion control algorithm that maintains stability for arbitrary network delay, capacity, load and topology.