Subject: Re: [Tsvwg] ECN-based TCP

From: Sally Floyd <[email-masked]>
Date: Wed, 17 Apr 2002 08:58:24 -0700

>Basically you can NOT rely on ECN by itself so that you can
>tell the difference between a drop due to error and a drop
>due to congestion... IMO... Sally what do you think?

Yep. 

This is stated in the ECN document, RFC3168, in Section 19.1:

"The CE codepoint of the ECN field is only used by routers as an
indication of congestion during periods of *moderate* congestion.
ECN-capable routers should drop rather than mark packets during heavy
congestion even if the router's queue is not yet full."

and is discussed in my short paper on "A Report on Some Recent
Developments in TCP Congestion Control", available from
"http://www.icir.org/floyd/papers.html".

- Sally

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