Re: [tsvwg] [Ecn-sane] Comments on L4S drafts

Jonathan Morton <> Fri, 19 July 2019 20:44 UTC

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From: Jonathan Morton <>
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Date: Fri, 19 Jul 2019 16:44:37 -0400
Cc: Wesley Eddy <>, Dave Taht <>, "De Schepper, Koen (Nokia - BE/Antwerp)" <>, "" <>, "" <>
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To: "Black, David" <>
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Subject: Re: [tsvwg] [Ecn-sane] Comments on L4S drafts
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> On 19 Jul, 2019, at 4:06 pm, Black, David <> wrote:
> To be clear on what I have in mind:
> 	o Unacceptable: All traffic marked with ECT(1) goes into the L4S queue, independent of what DSCP it is marked with.
> 	o Acceptable:  There's an operator-configurable list of DSCPs that support an L4S service - traffic marked with ECT(1) goes into the L4S queue if and only if that traffic is also marked with a DSCP that is on the operator's DSCPs-for-L4S list.

I take it, in the latter case, that this increases the cases in which L4S endpoints would need to detect that they are not receiving L4S signals, but RFC-3168 signals.  The current lack of such a mechanism therefore remains concerning.  For comparison, SCE inherently retains such a mechanism by putting the RFC-3168 and high-fidelity signals on different ECN codepoints.

So I'm pleased to hear that the L4S team will be at the hackathon with a demo setup.  Hopefully we will be able to obtain comparative test results, using the same test scripts as we use on SCE, and also insert an RFC-3168 single queue AQM into their network to demonstrate what actually happens in that case.  I think that the results will be illuminating for all concerned.

 - Jonathan Morton