From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x231.google.com (mail-lf0-x231.google.com [IPv6:2a00:1450:4010:c07::231]) (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 035C53B2A0; Tue, 19 Jan 2016 13:10:15 -0500 (EST) Received: by mail-lf0-x231.google.com with SMTP id 17so141828870lfz.1; Tue, 19 Jan 2016 10:10:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=Pu5kZgOr4w0W+zF18K+TN/XVWCPTrS+lFoqrt9C2b6E=; b=qXtS/AHNpVd4k22Yl2eIae7W1FE3aZdoxyo23T1+nvhgrxzcUe82io9xV+g66h7Z8I U5nycJL/L7jjXjhBzFWvcMi/+yRtlUa+eWJ3QV2d9Q8BaGnVClFUO5jY99vqv/ByBAgS 4Fa4qT1zmUWibQ9GNcsuoNA29hSGzXpLUKQQAeNGFe93SC5z4zS9I9eDCiP551CGgR0t YspIt2uLgDs3YF6Nmi9QDqjzlsZyGTH1aTxbAXnDro02j/p7WrZBuyLAT7IIGOmenjLj STM8QRUXX7tb/d8Ud3vdj8neWywkalmQZYNN5/t4RWv0UU5dHjhRuX5Z8COBraIXXelj gM4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:content-type:mime-version:subject:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to; bh=Pu5kZgOr4w0W+zF18K+TN/XVWCPTrS+lFoqrt9C2b6E=; b=nKozpXfDUjD7xq4ecJzUrMBDafF9M0RWiRTC68mJP7PLYtEVpfuxgTNeZz/1E6jcUL TIVoF9X50Cc4AR2owqA4UtpZwpjfmJUZ/pp1vJfjc+g6Z5MLd+n8uYIPdfE9NZjTaX99 T3rPoIXGsv6WNxqQIvCK9erF8ijYX7wT0qe3uGGt62kEFjC2R6Iu0ClbeAbbfmUyuA6R jnNy3KsO2kRdz4redJNIIDdr9lnbz+nHDj7Ls4lnfQAxu8EXPMiIIltrWDb1qnzi/eSp +9U/K2KRQcBi4icTOZkq0/ygSPii7Gc4JPd/jyXw0XmR1OUBbYS9DCv4VK0Xkyu86Y2Q Y+aA== X-Gm-Message-State: AG10YOTsoEr+XaPwiYP559X9qfk4VOhmEpLzGUfE2sONfO2vPnH+Hy2bc73yGwW+VUM/Rw== X-Received: by 10.25.15.29 with SMTP id e29mr11066178lfi.85.1453227014649; Tue, 19 Jan 2016 10:10:14 -0800 (PST) Received: from bass.home.chromatix.fi (37-33-99-74.bb.dnainternet.fi. [37.33.99.74]) by smtp.gmail.com with ESMTPSA id n62sm4141198lfn.5.2016.01.19.10.10.06 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 19 Jan 2016 10:10:14 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.2 \(3112\)) From: Jonathan Morton In-Reply-To: <7A2801D5E40DD64A85E38DF22117852C881A1224@wdc1exchmbxp05.hq.corp.viasat.com> Date: Tue, 19 Jan 2016 20:09:35 +0200 Cc: =?utf-8?Q?Dave_T=C3=A4ht?= , Jeff Weeks , "aqm@ietf.org" , "cake@lists.bufferbloat.net" , "codel@lists.bufferbloat.net" Content-Transfer-Encoding: quoted-printable Message-Id: References: <274D3A0FA900FD47AA6B56991AAA32FDC547FC0F@wtl-exchp-1.sandvine.com> <569D6DEA.9050603@taht.net> <7A2801D5E40DD64A85E38DF22117852C881A1224@wdc1exchmbxp05.hq.corp.viasat.com> To: "Agarwal, Anil" X-Mailer: Apple Mail (2.3112) Subject: Re: [Cake] [Codel] [aqm] codel with low shape rates X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 19 Jan 2016 18:10:16 -0000 > On 19 Jan, 2016, at 15:43, Agarwal, Anil = wrote: >=20 > (I would like very much to have an aqm that was knobless at these = speeds. Most of the work on trying to improve matters at these rates is = in the multitude of "cake" variants) Codel is pretty close to being self-tuning in terms of link capacity, as = long as it=E2=80=99s on the bottleneck and only needs to deal with one = flow per instance. The main trouble is when the inherent serialisation = delay becomes comparable to the time constants assumed for the total = estimated RTT. On very slow links, the a-priori RTT estimate needs to = be increased to account for that. Cake has an advantage here in knowing the link capacity, via its = built-in shaper. This is how it knows what fine-tuning to apply. = It=E2=80=99s hard for a =E2=80=9Cpure=E2=80=9D AQM qdisc to gather that = information automatically. With that self-tuning, Cake works usably well down to 64Kbps. At that = level, typical modern TCPs (especially CUBIC) saturate the link = continuously from the outset, so Codel ends up constantly signalling = them to slow down. With ECN on, this is harmless. - Jonathan Morton