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A New Internet-Draft is available from the on-line Internet-Drafts directories.
Title : DCLOR: De-correlated Loss Recovery using SACK option
for spurious timeouts
Author(s) : Y. Swami, K. Le
Filename : draft-swami-tsvwg-tcp-dclor-00.txt
Pages : 26
Date : 2002-10-29
A spurious timeout in TCP forces the sender to unnecessarily
retransmit one complete congestion window of data into the network.
In addition, TCP uses the rate of arrival of ACKs as the basic
criterion for congestion control. TCP makes the assumption that the
rate at which ACKs are received reflects the end-to-end state of the
network in terms of congestion. But after a spurious-timeout, the
ACKs don't reflect the end-to-end congestion state of the network,
but only a part of it. In these cases, the slow-start behavior after
a timeout can further add to network congestion instead of relieving
In this draft we propose changes to the TCP sender (no change is
needed for TCP receiver) that can be used to solve the problems of
both redundant-retransmission and network congestion after a spurious
timeout. These changes preserve the sanctity of congestion control
principles and are conservative in nature. The proposed
algorithm--called DCLOR--separates congestion control from loss
recovery, and uses the TCP SACK option to achieve this. DCLOR can be
used as a congestion control algorithm (after a spurious timeout) only,
and it can work with other spurious timeout detection mechanisms such
as the Eifel detection scheme.
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