A TCP ANALYSIS: IMPACT OF RECEIVER PERCEIVED INFORMATION ON THE PERFORMANCE OF TCP OVER Ad Hoc NETWORKS

An Ad hoc network is a completely wireless network with a dynamic nature of topology, which rapidly changes with time. Due to the node movement there are sudden losses of packets and delays. Transport protocols like TCP have been designed for reliable fixed networks. TCP misapprehend these packet losses as congestion in the network and call upon congestion control, which leads to avoidable retransmissions and loss in overall performance. In this work we propose a receiver information based approach, so that source can distinguish between route failure and network congestion. Simulation results show that the use of this feedback approach provides a significant improvement in performance. TCP does not differentiate between congestion and packet loss due to transmission errors or route failures, because it is designed for use over fixed low-error networks like the internet. In internet route failures and disruptions are very sporadic since network is fixed, therefore, packet losses, which is detected by TCP as a timeout, can be interpreted as a symptom of congestion in the network. A lot of research has been done on reliable transport protocols for cellular wireless networks. All the mechanisms proposed heavily depend on the presence of wired base station network, and hence cannot be directly applied to ad-hoc networks. In this work we study TCP performance over ad hoc networks and propose receiver information based feed back scheme, to control the TCP window at the sender side. TCP performance is tested in ad hoc network routed with DSR routing protocol, with two versions of TCP, TCP-new Reno, and TCP-feecon (proposed). With this study, we see number of unique characteristic of ad hoc networks for TCP, such as increasing ratio of out-of-order packet delivery, multiple competing connections contending for the bandwidth-constrained wireless channel and induce network congestion, mobility-induced disconnection, and reconnection. We propose an adaptive feed back technique which uses receiver information to command and control the sender side TCP window. Our implementation complexity is on the receiver side and is stable.