Data Transfer Efficiency Over Satellite Circuits Using a Multi-Socket Extension to the File Transfer Protocol (FTP)
Mark C. Allman, Shawn Ostermann, Hans Kruse · 1996
In several experiments using NASA's Advanced Communications Technology Satellite (ACTS), investigators have reported disappointing throughput using the TCP/IP protocol suite over 1.536Mbit/sec (T1) satellite circuits. A detailed analysis of FTP file transfers reveals that both the TCP window size, and the TCP "Slow Start" algorithm contribute to the observed limits in throughput. While it is tempting to approach a solution to this issue by raising the TCP window size, there are several issues which can not be addressed in that way: (1) In order to raise the TCP window size sufficiently to allow full utilization of a T1 circuit, the TCP Extended Window Option is required[4]. Commercial implementation of this option in major operating systems has not been completed. (2) The use of very large windows may actually hurt throughput if a moderate bit error rate is present on the satellite channel. (3) A change in the window size does not address the effect of the TCP Slow Start algorithm. We ...