Improving TCP/IP over geostationary satellite links

We focus in this paper on the undesirable phenomenon of early buffer overflow during slow start (SS) when TCP operates in large bandwidth-delay product networks such as those including geostationary satellite links. This phenomenon, already identified by Altman, Bolot, Nain, Elouadghiri, Erramdani, Brown and Collange (1995) and by Lakshman and Madhow (see IEEE/ACM Transactions on Networking, 1997) is caused by the bursty type of TCP traffic during SS. It results in an underestimation of the available bandwidth and a degradation in TCP throughput. Given the high cost and the scarcity of satellite links, it is of importance to find solutions to this problem. We propose two simple modifications to TCP algorithms and illustrate their effectiveness via mathematical analysis and simulations. First, we reduce the SS threshold in order to get in congestion avoidance before buffer overflow. Second, we space the transmission of packets during SS.