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

Jonathan Morton <> Fri, 26 February 2021 23:57 UTC

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From: Jonathan Morton <>
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Date: Sat, 27 Feb 2021 01:57:47 +0200
Cc: Bob Briscoe <>, TSVWG <>
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To: Martin Duke <>
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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 27 Feb, 2021, at 1:31 am, Martin Duke <> wrote:
> I wonder if the non-TCP ECN traffic is QUIC? I don't think the main implementations are doing it, but there are a few ECN-capable implementations in production.

This would be a reasonable interpretation of traffic on ports typically used with HTTP or similar L5 protocols.  We have, similarly, interpreted non-TCP traffic using ports commonly associated with tunnel protocols as actually being (at least partly) TCP through a tunnel.

However, most of what we saw was on random high ports, and some that are most often used by BitTorrent clients.  So we think it's probably due to BT clients trying to do "clever" things with TOS/DSCP but misunderstanding it.  I believe the default in libtorrent is to set CS1, correctly, so I don't know which particular clients might be so affected, or whether it is due to end users setting manual firewall mangle rules incorrectly.

Since the data collection tool we used doesn't have a way to unambiguously discriminate between QUIC and any other UDP-supported protocol, it's difficult for us to say more about how much QUIC-ECN was seen.  If you have a criterion we could use for that, we might be able to build it into a future run.

 - Jonathan Morton