Evaluating the Eifel Algorithm for TCP in a GPRS network

Andrei Gurtov
Reiner Ludwig

In Proceedings of European Wireless, February 2002, Florence, Italy. (Invited paper).

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Large and sudden variations in packet transmission delays are often unavoidable in GPRS. This may cause spurious timeouts in TCP. Spurious timeouts affect TCP performance in two ways: (1) the TCP sender unnecessarily reduces its load, and (2) the TCP sender is forced into a go-back-N retransmission mode. The Eifel algorithm avoids these consequences. We evaluate the performance of the Eifel algorithm for TCP Reno, NewReno and SACK in a simulated GPRS network. We use throughput and goodput as equally important performance metrics. In all our simulations, we find that the Eifel algorithm improves goodput; in some cases by up to 20 percent. When complemented with an efficient loss recovery scheme (SACK or NewReno), we find that the Eifel algorithm also improves bulk data download times in all our simulations; in some cases by up to 12 percent.