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Tutorials Program - SIGMETRICS 2001 / Performance 2001

TCP Congestion Controls: Algorithms and Optimization Models

Steven Low

CS & EE Depts
California Institute of Technology, Pasadena

Congestion control is a set of distributed algorithms to share network resources among competing users. They adapt to fluctuations in the capacity of, and the demand for, these resources. A TCP congestion control scheme consists of two subalgorithms: a queue management algorithm (e.g., DropTail, RED, REM etc) that provides congestion information to sources, and a source algorithm (e.g., Tahoe, Reno, NewReno, SACK, Vegas, etc) that adjusts window size in response.

In this tutorial, we will first briefly describe major TCP congestion control algorithms. Then we will explain several recently developed optimization models of these algorithms and use these models to understand, and predict network performance, such as stability, window dynamics, and fairness. We will focus on a duality model that treats source rates as primal variables, congestion measures as dual variables, and the process of congestion control as carrying out a primal-dual algorithm to maximize aggregate source utility subject to capacity constraints. We will illustrate how the duality model provides a unified framework to model and enhance various TCP congestion control schemes.

Who should attend?
Researchers and practitioners who are interested in learning about various TCP congestion control algorithms and their variants, and especially recent mathematical models of these algorithms.
Steven Low received his B.S. degree from Cornell University and PhD from the University of California -- Berkeley in 1992, both in electrical engineering. He has been a consultant to NEC, CA, in 1991 and was with AT\&T Bell Laboratories, Murray Hill, from 1992 to 1996, with the University of Melbourne, Australia, from 1996-2000, and is now an Associate Professor of the CS and EE Departments of Caltech. He has held visiting academic positions in the US, Hong Kong, and Australia. He was a co-recipient of the IEEE William R. Bennett Prize Paper Award in 1997 and the 1996 R&D 100 Award. He is on the editorial board of IEEE/ACM Transactions on Networking. He has been a guest editor of the IEEE Journal on Selected Area in Communications, on the program committee of several conferences. His research interests are in the control and optimization of communications networks and protocols, and network security and privacy.

[Last updated Tue Jan 2 2001]