End-to-End Performance Evaluation of Selected TCP Variants across a Hybrid Wireless Network

Reliable transport protocols such as TCP are tuned to perform well in traditional networks where packet losses occur mostly because of congestion. TCP is intended for use as a highly reliable end-to-end transport protocol for transporting applications such as World-Wide Web (WWW) between hosts in packet-switched computer communication networks. TCP was originally designed for wired links where the error rate is really low and actually assumed that packet losses are due to congestion in the network. However, the increasing popularity of wireless networks indicates that wireless links will play more important role in future internetworks but TCP performance in such networks suffers from significant throughput degradation and very high interactive delays. TCP responds to all losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy systems. Thus, in a bid to show and determine the possibility of adapting TCP protocol for optimal performance on the wireless link, this paper reviews and models the behaviors of TCP variants with a view to evaluate the end-to-end performance analysis of TCP versions: TCP Reno, TCP SACK and TCP Westwood (TCPW), which are designed to improve the performance of TCP in lossy networks. A wireless network model was developed using NS-2 network simulator which and the model was simulated. The results were analyzed in MATLAB 6.5 using throughput as a metric for comparison. The overall results indicate that TCP Westwood (TCPW) demonstrates better performance indices over other versions in a hybrid wireless network environment.