PERFORMANCE OF VARIOUS TCP IN VEHICULAR AD HOC NETWORK BASED ON TIMER MANAGEMENT
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Transmission control protocol (TCP) is one of the popular protocol in many applications which requires reliable end-to-end protocol. Improvement or replacement of TCP in wireless environments, unfortunately, studies have shown that TCP performance in Vehicular Ad-hoc Networks (VANETs) is very poor. TCP treats packet loss as a sign of network congestion. In wireless network however, losses can occur for reasons besides congestions, poor channel condition or collision. So TCP will reduce congestion window size, effectively decreasing throughput. In VANET, the path symmetry is not guaranteed due to high mobility. This can decrease TCP performance due to incorrect estimation of RTT times, resulting in unnecessary retransmission which produce excess of congestion in the network. The existing TCP variants cannot yield good performance in highly mobile environment due to the fact that TCP cannot able to differentiate packet drop occur from link failure with that of congestion in network. To overcome the problem of frequent retransmission, a Significant RTT timer modification to be made at the TCP sender side. The ultimate intend of the project is to design a new RTT, SRTT and RTO timers for high mobility environment (VANET). In this regard, an exclusive examination is being done with the existing RTT, SRTT and RTO timers under different TCP variants for vehicular network. The analysis was done with Bonn Motion mobility model that is built over NS-2 simulator. The TCP variants were evaluated with the metrics such as end-to-end delay, packet delivery factor, good put and throughput.