Dr. W. Timothy Strayer
Senior Scientist, Department of Internetwork Research
BBN Technologies

The popular perception is that TCP/IP does not run well over satellite networks, even though TCP/IP was designed with satellite networks in mind in the 1970s. Communication over satellites introduces a long delay (for GEOS, delay can be as much as 250 ms each way). This delay means there can be a lot of data in flight -- the so-called "delay-bandwidth product". But original TCP has known problems with a link with very large delay -- the window size is too small, the sequence space wraps too fast, and the acknowledgment scheme is too pedantic. Modifications to TCP to improve its overall performance while being fair to other connections, namely slow-start and congestion avoidance, do not work well as the delay or bandwidth or both increase. This talk will present the general problems with TCP and the fixes that have been applied, and consider how these fixes may help or hinder TCP/IP's performance over today's satellite networks. We will also discuss current and expected near future efforts to improve performance.