Re: [tsvwg] Fwd: New Version Notification for draft-heist-tsvwg-ecn-deployment-observations-00.txt

Jonathan Morton <> Fri, 19 February 2021 11:48 UTC

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From: Jonathan Morton <>
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Date: Fri, 19 Feb 2021 13:48:41 +0200
Cc: Pete Heist <>, TSVWG <>
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To: Mirja Kuehlewind <>
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Subject: Re: [tsvwg] Fwd: New Version Notification for draft-heist-tsvwg-ecn-deployment-observations-00.txt
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> On 19 Feb, 2021, at 1:44 pm, Mirja Kuehlewind <> wrote:
> I have one question on the data. Maybe I'm not readying this correctly but if I look at the big table at the end, then I see a lot of cases where there are much more CE marks than ECT(0) marks. That's a bit unexpected as usually an AQM should only mark a small portion of the packets. Or do I interpret the data there incorrectly?

We believe that's evidence of the ECN field being used incorrectly by some UDP-based applications.  This is discussed in the draft and could be due to people putting values intended for the DSCP field (6 bits, left justified) or the obsolete Precedence-TOS fields (3+4 bits, left justified) directly into the TOS byte.

For that reason, we only count TCP and what are probably tunnelled TCP traffic as evidence of actual ECN and AQM deployment.

 - Jonathan Morton