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

Jonathan Morton <chromatix99@gmail.com> Wed, 18 November 2020 06:45 UTC

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From: Jonathan Morton <chromatix99@gmail.com>
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Date: Wed, 18 Nov 2020 08:45:25 +0200
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Cc: "De Schepper, Koen (Nokia - BE/Antwerp)" <koen.de_schepper@nokia-bell-labs.com>, tsvwg IETF list <tsvwg@ietf.org>
To: Sebastian Moeller <moeller0@gmx.de>
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Subject: Re: [tsvwg] new tests of L4S RTT fairness and intra-flow latency: defaults ready for testing
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> On 18 Nov, 2020, at 8:21 am, Sebastian Moeller <moeller0@gmx.de> wrote:
> 
> The changes that Oliver submitted to TCP Prague not only increase the fudge RTT to 25ms, but they also, as Koen mentioned, increase the time it takes for Prague to switch to the new fairness mode to 500 RTTs, or 5 seconds at 10ms RTT.
> I really wonder how that affects fairness if the shallow queue is used by a bunch of short flows with 10ms RTT. As far as I can tell the consequences of this delayed engagement have not been described properly. 

Yes, that engagement delay is clearly visible in a time-series plot.  I think it may even be more than 5 seconds in practice:



 - Jonathan Morton

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