From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-x32f.google.com (mail-ot1-x32f.google.com [IPv6:2607:f8b0:4864:20::32f]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 115CC3B29E for ; Mon, 24 Jun 2019 17:25:48 -0400 (EDT) Received: by mail-ot1-x32f.google.com with SMTP id s20so15073440otp.4 for ; Mon, 24 Jun 2019 14:25:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=PoILjhmQzb1AKGplhfDPt0thdnxoyVJohPc/qIGz/lw=; b=UTTq0siKE4cevwlCwlRIDnLYpLgAYGmg2fbOMVYDOVfNmi10MfN1ujmwhUurr2kVqI Wx85BydwB46qi5O37NJEw8KOa6X13Zem2HPJmt6ZI/lveT2g5kJbdlsBGFhhbj1g1epD W7mp0yKvrQpj93ldPfEamFSw8UVBUn8LiSDjfZ1tO1scYCBcP+kz7ZKEmpsapc7az55m XbqVZ//VgGtELpvhv0uJZ15sLgxs1dOP9ru+EqNH0Md/LoN8JCTw+zu+NWF5bnam2TNA 113eYxAkqkBV/diE6LWMfvX9WvWVRWp3DPq0zXtoQnxoAdYUi5YR4OTEqIUlXZYh9Y29 f1SA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=PoILjhmQzb1AKGplhfDPt0thdnxoyVJohPc/qIGz/lw=; b=VKEAGsalsieYLQasexdZHt8YIa9cfuO9KbFiugj8gW6xxIrHuovrPXJ0npWx/4tQ9z A2mQGoVRXW1wqDHkVyJZEUJbiOZ8jRETDsH3a9ZmmekYzZG8KTPFdSJASFkJY7+uN8x0 OTDzZAAJxE5HyPsEoyL+tQIAaEa12uteQZ7K9hLyUG6cVwzEGODuew+Mtt0KFeJCGOgs dFp/E/yzGYVImTT3naOcgKIKX9Fen8tLdqM7GNvW2ghZ3edPdjC6ktVPKAqXIy+j716N 0ODy4h8A3LRWH51PI9Nt7u97JPmFSwtuINHpkZlQoLyOt1qTpNLzAmmBVguZsD/pW7eJ JiLw== X-Gm-Message-State: APjAAAU/NwZ4MFsfELkjRYgFtinE+5K11XBNUZKZc2NqprIxfd6omKKH AJu/0hpuMTntaU8/zRve+d9IgV+TOJJElagngLE= X-Google-Smtp-Source: APXvYqx5t73YkQPiBiPsL1EuPR+kXxSWn/6dNsXp4yXLOU9yVAdmTb1TjirKezVl4jL0u90jtP2QyOC7KVs1I5trE+8= X-Received: by 2002:a9d:470f:: with SMTP id a15mr51770308otf.235.1561411547348; Mon, 24 Jun 2019 14:25:47 -0700 (PDT) MIME-Version: 1.0 References: <350f8dd5-65d4-d2f3-4d65-784c0379f58c@bobbriscoe.net> <46D1ABD8-715D-44D2-B7A0-12FE2A9263FE@gmx.de> <835b1fb3-e8d5-c58c-e2f8-03d2b886af38@gmail.com> <1561233009.95886420@apps.rackspace.com> <71EF351D-AFBF-4C92-B6B9-7FD695B68815@gmail.com> <1561241377.4026977@apps.rackspace.com> <081BAF4F-2E1C-441B-A31A-9AC70E3EDA32@gmail.com> <1561402678.523819778@apps.rackspace.com> <7F847464-70DD-4F9F-8CA5-DD3C8B65689C@gmail.com> In-Reply-To: <7F847464-70DD-4F9F-8CA5-DD3C8B65689C@gmail.com> From: Luca Muscariello Date: Mon, 24 Jun 2019 23:25:35 +0200 Message-ID: To: Jonathan Morton Cc: "David P. Reed" , "ecn-sane@lists.bufferbloat.net" , Brian E Carpenter , tsvwg IETF list Content-Type: multipart/alternative; boundary="000000000000a0c23b058c18745b" Subject: Re: [Ecn-sane] [tsvwg] per-flow scheduling X-BeenThere: ecn-sane@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion of explicit congestion notification's impact on the Internet List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 24 Jun 2019 21:25:48 -0000 --000000000000a0c23b058c18745b Content-Type: text/plain; charset="UTF-8" On Mon, Jun 24, 2019 at 9:32 PM Jonathan Morton wrote: > > On 24 Jun, 2019, at 9:57 pm, David P. Reed 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, even if it is news to nobody, AIMD does not necessarily converge to a limit cycle (e.g. a sawtooth). It depends on some regularity conditions of the AIMD law and congestion feedback too. For instance, AIMD delay based congestion control or AIMD with certain ECN laws may display no limit cycles. Still under certain conditions. Just to recall that the problem is a little more complex than that in general. > > - Jonathan Morton > _______________________________________________ > Ecn-sane mailing list > Ecn-sane@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/ecn-sane > --000000000000a0c23b058c18745b Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


=
On Mon, Jun 24, 2019 at 9:32 PM Jonat= han Morton <chromatix99@gmail.c= om> wrote:
> On 24 Jun, 2019, at 9:57 p= m, David P. Reed <dpreed@deepplum.com> wrote:
>
> TCP doesn't have a "natural sawtooth" - that is the resp= onse 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 evol= ution that *doesn't* resemble a sawtooth, regardless of the congestion = signalling employed.=C2=A0 And I will show you that it either has severe un= derutilisation of the link, or is using SCE signals.=C2=A0 The sawtooth is = characteristic of the AIMD congestion control algorithm.

Jonathan,
even if it is news to nobody,
AIMD does not necessarily converge to a limit cycle (e.g. a sawtooth). I= t depends on =C2=A0some regularity conditions of the AIMD law and congestio= n feedback too.
For instance, =C2=A0AIMD delay based congestion c= ontrol or AIMD with certain =C2=A0ECN laws may display no limit cycles. Sti= ll under certain conditions.
Just to recall that the problem is a= little more complex than that in general.

=C2=A0<= /div>

=C2=A0- Jonathan Morton
_______________________________________________
Ecn-sane mailing list
Ecn-san= e@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/ecn-sane
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