TCP gateway design considerations for satellite link blockage mitigation

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 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.