ACK delay control for improving TCP throughput over satellite links

TCP has been proved to work well in a variety of situations. However, in links of large bandwidth products, e.g., satellite links, TCP might underutilize the link and degrade the reliability. A number of revised algorithms have been proposed to improve TCP performance. In this paper, we propose a new algorithm to improve TCP throughput without modifying the TCP protocol. Since TCP uses acknowledgements (ACKs) to adjust the sending rate, the basic idea of our scheme is to delay (or shape) ACKs traveling through a node where the forward connection is congested. The algorithm aims to fully eliminate packet loss caused by buffer overflow. We implement this scheme in the intermediate nodes connecting satellite links and make a simulation study on its effect. In addition, we test the proposed algorithm in the real world. The results of both simulation and tests show that the proposed scheme improves the TCP throughput by effectively controlling the acknowledgment flow.