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Re: [tsvwg] new tests of L4S RTT fairness and intra-flow latency

"alex.burr@ealdwulf.org.uk" <alex.burr@ealdwulf.org.uk> Sun, 15 November 2020 13:08 UTC

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Date: Sun, 15 Nov 2020 13:06:40 +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: tsvwg IETF list <tsvwg@ietf.org>, Pete Heist <pete@heistp.net>
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In-Reply-To: <d2edb18dd3cbfecce0f70b3345e4ea70a0be57b9.camel@heistp.net>
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Subject: Re: [tsvwg] new tests of L4S RTT fairness and intra-flow latency
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Hi Pete,
 Interesting data. 
Maybe I've missed it, but I don't see whether these tests were run against a version of TCP-Prague having the RTT-independence workaround mentioned during interim-2020-tsvwg-01 [1], and if so what its mode was. Can you clarify that?

Thanks,
Alex

[1] Slide 16 of https://datatracker.ietf.org/meeting/interim-2020-tsvwg-01/materials/slides-interim-2020-tsvwg-01-sessa-l4s-tcp-prague-update-00.pdf



 On Thursday, November 12, 2020, 9:03:17 PM GMT, Pete Heist <pete@heistp.net> wrote: 



Hi,

We have posted some new tests of L4S here:

https://github.com/heistp/l4s-tests

These tests cover two-flow fairness in several qdiscs with different
path RTTs per-flow, and transient behavior in fq_codel queues.

The results raise some concerns about a bias in favor of L4S flows in
DualPI2 queues, throughput imbalances between flows with different path
RTTs, and intra-flow latency spikes upon rate reductions in fq_codel.
The repo above contains a walk-through of the key findings, and links
to more results in the Appendix.

Regards,
Pete

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