Improving TCP Performance in Asymmetric Wireless Networks

D. Kim and H. Bae (Korea)


Asymmetric Networks, TCP, Forwardand Backward Path Delay Estimation.


Many networks exhibit the asymmetric character istics in terms of bandwidth, medium access, loss rate and acquired route. Even in these asymmetric networks, TCP has been accepted for supporting reliable end-to-end Internet services. However, since TCP is a transport pro tocol that uses feedback information like ACK messages, late arrival or absence of the ACK packets results in the sender invoking congestion control procedures. This reduces the transmission rate since the sender mistook that there occurs a packet loss due to network congestion. If the timeout event at the sender is solely caused by the fluctuation in end-to-end delay and and not by the packet loss, we should compensate for the reduction of transmis sion rate when the corresponding ACK arrives behind its schedule. Due to the presence of asymmetric delays for each flow in a path, we enhance TCP to consider separate delays for each flow in the path. Through simulations, we confirm that our enhanced TCP outperforms current TCP significantly when end-to-end delay fluctuation is high.

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