Understanding TCP Vegas: A Duality Model*

Abstract:

*This Technical report is an updated version of TR-616-00

This paper presents a model of the TCP Vegas congestion control
mechanism as a distributed optimization algorithm. Doing so has three
important benefits. First, it helps us gain a fundamental understanding
of why TCP Vegas works, and an appreciation of its limitations. Second,
it allows us to prove that Vegas stabilizes at a weighted proportionally
fair allocation of network capacity when there is sufficient buffering
in the network. Third, it suggests how we might use explicit feedback
to allow each Vegas source to determine the optimal sending rate when
there is insufficient buffering in the network. In addition to
presenting the model and exploring these three issues, the paper
presents simulation results that validate our conclusions.