Analysis and improvement of fairness between TCP Reno and Vegas for deployment of TCP Vegas to the Internet

摘要

According to past research, a TCP Vegas version is able to achieve higher throughput than TCP Tahoe and Reno versions, which are widely used in the current Internet. However we need to consider a migration path for TCP Vegas to be deployed in the Internet. In this paper, by focusing on the situation where TCP Reno and Vegas connections share the bottleneck link, we investigate the fairness between two versions. From the analysis and the simulation results, we find that the performance of TCP Vegas is much smaller than that of TCP Reno as opposed to an expectation on TCP Vegas. The RED algorithm improves the fairness to some degree, but there may still be an inevitable trade-off between fairness and throughput. Accordingly, we consider two approaches to improve the fairness. The first one is to modify the congestion control algorithm of TCP Vegas, and the other is to modify the RED algorithm to detect misbehaved connections and drop more packets from those connections. We use both of analysis and simulation experiment for evaluating the fairness, and validate the effectiveness of the proposed mechanisms.