Adaptive Flow Control: An Extension to Delayed Fast Recovery

The integration of wireless links (terrestrial and satellite) with terrestrial wired networks has been a subject of extensive research keeping in view the performance issues of TCP with wireless links. Performance improvement in SACK TCP has been shown earlier by delaying fast recovery. However, the technique of delayed fast recovery just avoids flow control in case of random loss. If congestion cannot be ruled out, the technique triggers fast recovery and reduces congestion window conventionally without considering degree of congestion in the network. In this paper, an extension to delayed fast recovery algorithm is presented, which determines TCP flow depending on the estimation of congestion. The proposed scheme preserves conventional loss recovery and decouples TCP flow control, which depends on the displacement between two consecutive losses. Simulation based experiments demonstrate noticeable performance improvement with modified SACK TCP on large delay erroneous links. However, the performance is comparable in case of conventional terrestrial wired networks where losses due to congestion are common.