Making TCP Robust Against Delay Spikes

Andrei Gurtov

University of Helsinki, Department of Computer Science, Series of Publications C, No C-2001-53, November 2001.

[Full Text in PDF Format, 88KB]


This document discusses optimizations for a TCP sender that are most helpful in the presence of delays spikes, but are seemingly suitable for general deployment. The motivation for this work is increasing popularity of links (e.g. provided by cellular networks) that have delay spikes exceeding the usual link latency by several times. The effect of a delay spike on TCP Tahoe, Reno, NewReno and SACK is described. The document recommends timing every segment and restarting the retransmit timer to achieve a more conservative RTO estimate. Furthermore, it discusses how a series of DUPACKs should be treated.