Tcp/rlp Coordination and Interprotocol Signaling for Wireless Internet

We investigate the interactions of two distinct loss recovery mechanisms employed by TCP and IS-707, a partial error recovery Radio Link Protocol (RLP), during a long-time, low-speed TCP connection over a radio channel with correlated losses. In such a scenario not only the unrecovered frame losses, but also the slow RLP frame loss recovery mechanism trigger the TCP congestion avoidance, resulting in very poor system performance in high frame error regime. A run-time coordination of the RLP and TCP can mitigate this problem. An improvement of IS-707 RLP consisting of the addition of a limited number of probing frames after a TCP segment transmission is proposed to speed up frame loss recovery. That modification alone can very significantly improve TCP throughput in the high frame loss regime with weak correlations, but cannot equally well cope with the effects of consecutive TCP packet losses. Further improvement of TCP throughput in the latter case might be obtained by reducing the maximum TCP retransmission timeout RTOmax, to the extent that it keeps the network stable. The proposed TCP–RLP coordination mechanisms can be supported by interprotocol signaling.