Effectiveness of TCP SACK, TCP HACK and TCP Trunk over satellite links

Abstract

This paper reports the study on the performance enhancements of two extensions to the standard TCP implementation - Selective Acknowledgement (SACK) and Header Checksum (HACK) - over satellite links that are characterized by high latency and high bit error rate. We also examine the effectiveness of TCP Trunk, an edge-to-edge aggregation and congestion control mechanism, over the satellite link. Our study on the effect of varying the TCP window size over long latency link for New Reno, SACK, HACK and TCP Trunk implementations show that increasing window size does improve the performance, but only up to a certain value of the window size, and a further increase actually reduces the performance. Other interesting observations from our experimental study are: SACK enabled TCP Trunk across the satellite link edge routers can improve the throughput regardless of the end host TCP implementation; disabling the link layer CRC and instead implementing the HACK extension to the TCP (and of course HACK+ SACK) can improve the throughput further.