Abstract: The standard implementation of TCP experiences heavy throughput degradation when packets arc reordered.This paper presented a new version of the TCP protocol, called TCP_ D, which improves its performance to mobile-in-duced reordering packets in mobile ad hoc network (MANET). In TCP_D,the response to the receipt of duplicate acknowledgement is delayed by a short period to allow the receiver to receive the packets that travel in different path. We analyzed TCP_D to show that its steady state throughput is similar to the native implementations of TCP when packet reordering does not occur. I}he simulation results show that TCP_D performs consistently better than standard implementations of TCP under persistent packets reordering. In the case that packets are not reordered TCP_D maintains the same throughput as typical implementation of TCP ( TCP-NewReno) and shares network resource fairly.

Key words: Congestion control,MANET, TCP, Throughput