Understanding TCP Vegas: Theory and Practice

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. 1 Introduction TCP Vegas was introduced in 1994 as an alternative source-based congestion control mechanism for the Internet [10]. In contrast to the TCP Reno algorithm, which induces congestion to learn the available network capacity, a Vega..