The Eifel Algorithm: Making TCP Robust Against Spurious Retransmissions
Randy H. Katz
Appears in ACM Computer Communications Review, Vol. 30, No. 1, January 2000.
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We propose an enhancement to TCP’s error recovery scheme, which we call
the Eifel algorithm. It eliminates the retransmission ambiguity, thereby
solving the problems caused by spurious timeouts and spurious fast retransmits.
It can be incrementally deployed as it is backwards compatible and does
not change TCP’s congestion control semantics. In environments where spurious
retransmissions occur frequently, the algorithm can improve the end-to-end
throughput by several tens of percent. An exact quantification is, however,
highly dependent on the path characteristics over time. The Eifel algorithm
finally makes TCP truly wireless-capable without the need for proxies between
the end points. Another key novelty is that the Eifel algorithm provides
for the implementation of a more optimistic retransmission timer because
it reduces the penalty of a spurious timeout to a single (in the common
case) spurious retransmission.