A COMPARISON OF MECHANISMS FOR IMPROVING TCP PERFORMANCE OVER WIRELESS LINKS

Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly because of conge stion, However, networks with wireless and other lossy links also suff er from significant losses due to bit errors and handoffs. TCP respond s to all losses by invoking congestion control and avoidance algorithm s, resulting in degraded end-to-end performance In wireless and lossy systems, In this paper, we compare several schemes designed to improve the performance of TCP in such networks, We classify these schemes in to three broad categories: end-to-end protocols, where loss recovery i s performed by the sender; link-layer protocols that provide local rel iability; and split-connection protocols that break the end-to-end con nection into two parts at the base station, We present the results of several experiments performed in both LAN and WAN environments, using throughput and goodput as the metrics for comparison. Our results show that a reliable link-layer protocol that is TCP-aware provides very g ood performance, Furthermore, it is possible to achieve good performan ce without splitting the end-to-end connection at the base station, We also demonstrate that selective acknowledgments and explicit toss not ifications result in significant performance improvements.