Re: [tsvwg] L4S status: #17 Interaction w/ FQ AQMs

"alex.burr@ealdwulf.org.uk" <alex.burr@ealdwulf.org.uk> Thu, 07 November 2019 12:54 UTC

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Date: Thu, 07 Nov 2019 12:54:44 +0000
From: "alex.burr@ealdwulf.org.uk" <alex.burr@ealdwulf.org.uk>
Reply-To: "alex.burr@ealdwulf.org.uk" <alex.burr@ealdwulf.org.uk>
To: Greg White <g.white@cablelabs.com>, Jonathan Morton <chromatix99@gmail.com>
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Subject: Re: [tsvwg] L4S status: #17 Interaction w/ FQ AQMs
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    On Thursday, November 7, 2019, 3:35:06 AM GMT, Jonathan Morton <chromatix99@gmail.com> wrote:  

> > - if the CoDel queue is upgraded to perform Immediate AQM on L4S flows, the latency spike can be largely avoided.

> This is not relevant, since the point of this exercise is to establish the extent of L4S' compatibility with existing, unmodified networks, in which Codel happens to be the most widely deployed > AQM.  You cannot reasonably expect the entire Internet to "upgrade" to L4S compatible AQMs before you can safely begin deployment.

I wonder if Codel actually is the most widely deployed AQM. This is not to dispute your point, which is correct - proposing an update to Codel doesn't addess existing deployments.It's just that I'm aware that there is an awful lot of kit out there which has an implementation of RED (or WRED) in hardware - eg for TR-059 [1], which mandates WRED support in BRAS. That's from having worked at a silicon vendor, so it doesn't give me visibility of actual usage. I understand a lot of it isn't switched on, but if even a small fraction of it was, it would be a pretty big deployment. It would be interesting if anyone has actual numbers. .  Of course, to be relevant to this discussion, it would need to be configured to do ECN marking as well. 

[1] https://www.broadband-forum.org/technical/download/TR-059.pdf
Alex