TCP Gateway Design Considerations for Satellite Link Blockage Mitigation

Phillip A. Spagnolo, Thomas R. Henderson, Jae H. Kim, and Gerald T. Michael

IEEE International Communications Conference (ICC), May 2003.

Abstract: We study the performance of TCP over a satellite link, which is subject to intermittent blockages.  Our simulation-based study characterizes the performance degradation of transferring messages ranging from small web objects to large files over satellite channels with widely varying blockage statistics.  Using a split connection gateway, we investigate the impact of trying to preserve TCP end-to-end semantics upon connection close and find that such an approach significantly reduces the ability of small TCP transfers to survive a long duration blockage.   We show that by tying the satellite gateway's offered window to the terrestrial TCP sender to the space in the send buffer on the satellite side, and by quickly responding when the satellite link becomes available, the split-connection gateway can essentially eliminate the delay incurred waiting for the TCP persist timer to expire.  Finally, we illustrate how aspects of the gateway's design affect large and small TCP transfers differently.