Adaptive end-to-end loss differentiation scheme for TCP over wired/wireless networks

We improve a well-known TCP throughput enhancement scheme over heterogeneous networks of wired/wiress paths. The scheme (Westwood+) adjusts the congestion window using the estimate of currently available bandwidth instead of halving the window in the event of a packet loss, enhancing the TCP throughput. Our scheme infers the cause of packet loss(if it is due to congestion or regular bit errors over wireless paths) from the changes of the RTT values. We adapt the RTT threshold used for determining the cause of packet loss to the current congestion level. For example, we increase the RTT threshold for a packet loss to be regarded as due to congestion when the congestion level of the path is estimated to be low. This avoids unnecessary halving of the congestion window on packet loss due to regular bit errors over wireless path in a more precise way than previous schemes. Compared with the Westwood+, our scheme improves the TCP throughputs by 29% and 55% on 1 Mbps and 10 Mbps paths, respectively. The fairness degradation is negligible.