A tunable slow start for TCP

Abstract

Recently, there has been an interest in accelerating the initial bandwidth discovery phase of TCP. In this paper the feedback provided by TCP Acknowledgements (ACKs) does not only mean (as in legacy TCP) that a single data packet has gone out of the network, but also that new data packets can be sent in bursts as opportunistically indicated by the receiver. For this purpose, regular ACKs can be split so that an acknowledged portion of a segment instructs the sender to open more aggressively its congestion window. This article details the implementation and testing of ACK division which has been used so far to compensate the effect on TCP performance of random losses, spurious timeouts and handovers at transport level. We specifically show the benefits of using the ACK division in slow start for long delay networks.