EXPLICIT LOSS NOTIFICATION SCHEMES FOR IMPROVING TCP PERFORMANCE OVER WIRELESS NETWORKS

Abstract

TCP is designed to perform well in traditional wired networks with the assumptions that packet losses are mainly due to network congestion and random bit error rate (BER) is negligible. However, wireless networks suffer from significant packet losses due to high bit error rate and handoffs. Hence TCP performs poorly in wireless networks because it treats any packet loss in the network to be a result of network congestion and slows down its transmission rate. In order to find effective solutions to this effect, TCP sender should know the cause of packet loss and react to those losses appropriately. For many years, a large number of techniques have been proposed and implemented for improving TCP performance over wireless networks. But an efficient technique is one which requires fewer modifications at the intermediate nodes in the network. In this Dissertation entitled "EXPLICIT LOSS NOTIFICATION SCHEMES FOR IMPROVING TCP PERFORMANCE OVER WIRELESS NETWORKS ", we propose two schemes which detect wireless packet loss and notifies TCP sender about cause of the loss. The base station feedback scheme implements loss detection proxy at base stations which monitors incoming packets and acknowledgements. Using TCP header information in the arriving packets, it detects wireless packet loss and notifies TCP sender using one of the reserved flag bit in TCP header. The inter-arrival time based receiver feedback scheme detects wireless packet loss at the receiver using inter-arrival time gap between consecutive packets. In both schemes, we modified TCP Reno's congestion control algorithm to react to congestion and wireless losses appropriately. The proposed loss detection schemes have been simulated using widely known and available Network Simulator NS-2 on a Linux based platform. Their performance has been compared with TCP and Reno protocols for various loss rates. Results show that the proposed schemes have significant throughput gain over TCP and Reno protocols. 111