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TCP-PLDR: A Novel Packet Loss Detection and Response Mechanism for TCP in Mobile Ad Hoc Networks
Henock Mulugeta Melaku, Kumudha Raimond And Dereje Hailemariam Woldegebreal

Mobile ad hoc network (MANET) has provided new challenges, which affect the end-to-end transmission of data. In MANET, data packets can get lost due to congestion, route failure, or wireless channel error. Transmission control protocol (TCP) performs poorly in such networks. This is because TCP’s congestion control mechanism cannot distinguish between congestion and non-congestion related packet losses. TCP was previously developed for wired networks with the assumption that packet loss is an indication of congestion. However, in MANET TCP performs congestion control action for several types of losses that are not related to congestion. Consequently, when a packet loss is detected either by timeout or three duplicate acknowledgments, TCP slows down the sending rate by adjusting its congestion window size (cwnd) and unnecessarily retransmit a packet, which leads to lower throughput. In this paper, we proposed a novel approach for TCP to distinguish packet losses due to congestion or route failure due to mobility of nodes. The proposed protocol is called TCP Packet Loss Detection and Response (TCP-PLDR). We developed analytical model of throughput of TCP with selective acknowledgment (TCP-SACK) and TCP-PLDR protocols in the presence of congestion and route failure losses. Simulation was conducted using network simulator (ns-2) and results showed that TCP-PLDR improves TCP-SACK’s performance in MANET. As an example, simulation experiment for route failure and congestion loss scenario shows that TCP-PLDR improves the throughput of TCP-SACK on average by 39%.

Keywords: MANET, TCP, TCP-PLDR, TCP-SACK, route failure, congestion, packet loss.

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