A study of a high speed packet scheduling method for achieving fairness among TCP connections

In this paper, we first investigate the fairness between TCP Reno and TCP Vegas by focusing on the situation where Reno and Vegas connections share the bottleneck link. 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 still be an inevitable trade-off between fairness and throughput. Accordingly, we propose a ZL-RED (Zombie Listed RED) algorithm, which enhances the RED algorithm to provide fair service for many flows at the bottleneck router. ZL-RED uses the Zombie List, which has been originally proposed by SRED, to detect mis-behaving flows which send packets at higher rate than others. Then, ZL-RED sets higher packet discarding probabilities for those mis-behaving flows. We evaluate an effectiveness of ZL-RED by simulation experiments, and show that ZL-RED can actually improve fairness among TCP connections.