The Eifel Retransmission Timer

Reiner Ludwig
Keith Sklower

Appears in ACM Computer Communications Review, Vol. 30, No. 3, July 2000.

[Full Text in PDF Format, 464KB]


We analyze two alternative retransmission timers for the Transmission Control Protocol (TCP). We first study the retransmission timer of TCP-Lite which is considered to be the current de facto standard for TCP implementations. After revealing four major problems of TCP-Liteís retransmission timer, we propose a new retransmission timer, named the Eifel-Xmit-Timer, that eliminates those problems. The strength of our work lies in its hybrid analysis methodology. We develop models of both retransmission timers for the class of network-limited TCP bulk data transfers in steady state. Using those models, we predict the problems of TCP-Liteís retransmission timer and develop the Eifel-Xmit-Timer. We then validate our model-based analysis through measurements in a real network that yield the same results.