Subject: [Tsvwg] [DCLOR] A new Internet Draft on congestion control after spurious timeouts

From: [email-masked]
Date: Wed, 30 Oct 2002 11:30:26 -0600

Hi,

Couple of days back we submitted a new Internet Draft with the title "DCLOR: De-correlated Loss recovery using SACK option for spurious timeouts," that talks at length about network congestion after spurious timeouts. It's now available at:
http://www.ietf.org/internet-drafts/draft-swami-tsvwg-tcp-dclor-00.txt

The draft is slightly long (26 pages including the appendix), but we believe the problem of network congestion after a spurious timeout has largely been ignored, and we have taken all the space we could to make our point. I'd request you to read it inspite of the length.

The draft also advocates a new mechanism for spurious timeout detection, but it can be used as a congestion control algorithm only and can rely on other spurious timeout detection mechanism such as the Eifel detection scheme. 

We also provide results of our experiments in the appendix of the draft. The results compare the performance of Eifel, FRTO and DCLOR (and there are some surprises in store).  

We will be very grateful for your feedback and suggestions.

Thanks
Best regards
Yogesh

Following is the abstract of the draft:

Abstract
   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
   it.
   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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