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Re: [tsvwg] [Ecn-sane] per-flow scheduling

Jonathan Morton <chromatix99@gmail.com> Mon, 24 June 2019 19:32 UTC

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From: Jonathan Morton <chromatix99@gmail.com>
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Date: Mon, 24 Jun 2019 22:31:56 +0300
Cc: Brian E Carpenter <brian.e.carpenter@gmail.com>, "ecn-sane@lists.bufferbloat.net" <ecn-sane@lists.bufferbloat.net>, tsvwg IETF list <tsvwg@ietf.org>
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To: "David P. Reed" <dpreed@deepplum.com>
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Subject: Re: [tsvwg] [Ecn-sane] per-flow scheduling
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> On 24 Jun, 2019, at 9:57 pm, David P. Reed <dpreed@deepplum.com> wrote:
> 
> TCP doesn't have a "natural sawtooth" - that is the response of TCP to a particular "queueing discipline" in a particular kind of a router - it would respond differently (and does!) if the router were to drop packets randomly on a Poisson basis, for example. No sawtooth at all.

I challenge you to show me a Reno or CUBIC based connection's cwnd evolution that *doesn't* resemble a sawtooth, regardless of the congestion signalling employed.  And I will show you that it either has severe underutilisation of the link, or is using SCE signals.  The sawtooth is characteristic of the AIMD congestion control algorithm.

 - Jonathan Morton

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