TCP Westwood+ congestion control

TCP Westwood+ is a sender-side only modification of the TCP Reno/NewReno classic congestion control protocol stack that optimizes the performance of TCP congestion control especially over wireless networks. TCPW is based on end-to-end bandwidth estimation to set congestion window and slow start threshold after a congestion episode, that is, after three duplicate acknowledgments or a timeout. The bandwidth is estimated by properly low-pass filtering the rate of returning acknowledgment packets. The rationale of this strategy is simple: in contrast with TCP Reno, which blindly halves the congestion window after three duplicate ACKs, TCP Westwood+ adaptively sets a slow start threshold and a congestion window which takes into account the bandwidth used at the time congestion is experienced. TCP Westwood significantly increases fairness wrt TCP (New) Reno in wired networks and throughput over wireless links.



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