From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x236.google.com (mail-lf0-x236.google.com [IPv6:2a00:1450:4010:c07::236]) (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 D0A253B2B9; Sat, 4 Jun 2016 02:23:36 -0400 (EDT) Received: by mail-lf0-x236.google.com with SMTP id w16so66487836lfd.2; Fri, 03 Jun 2016 23:23:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=jOqwUuYsDKbjEFYWIVHVLLiCkP9YHmOTvRTuEa2l5n4=; b=RreT9xk6cbG7KM5SU1mn0N5c7F+wYGWmeo+y3laulVh6IdRok+3ilrpnRWMhmayAXw VlPBrcAML10Z4W8gCIHq0drBC3+0tkqxxX/2ZJpaNO43h5hamFa2g3jHBYASIchlo1Dn wde5HZSeFS9yJ3yITSvGVTM6wbvp5FjzuOAT2vDMgTXd6Ezo+ZtvD6q5vtXBzLIlNC3M wSFWpN4znnZNyZkP1fT097hRtCdvAyEyzhXWP87jDr3OhpY+OGIjT08tZJpqJu7zQDHY T8ATa9cPbcsr5gnq0MiocNOAZKqz/E/AbXRDSKX8zn62tbsTh6W0ATbK6nGeuIIcqZeI 56XA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=jOqwUuYsDKbjEFYWIVHVLLiCkP9YHmOTvRTuEa2l5n4=; b=VRF31nCctFD3ANbjrJGufw5iGK96atoBlRHtAm/H4nz3/+kKiJSkN0sqTNutEG3jAY Za9vbtV3xY64tI5qViym5Z8d3Tzm88JpxpSEY963sDprFat0u+x8lJaIOPmUtGtFVGcC 0HNrzCQECuFi7+aYl9SPUsQgHjJtH2ASct1dT/x9iuyACBhf6oBxLEJIrJRt2uygl5Nk I11RBHN5GKSb9B/xlJu7Bd6ROo3qbJqM4YV9u9WmR2Fcxx8i7+o6sQTii5I49gD0WaWT 35vrWXksgHEQ2Z4KmXP0yRKBHlc1xcHQyG3+/0dvtCk0eztQTzdAhSkWaBzkIiKllVDg 9O4Q== X-Gm-Message-State: ALyK8tJH3Wd2OHbepGlKNsXTtzUJ/HZSUrW/Ru/wMmOlGveRhAMHj/kN18ltJcfbIIIpNQ== X-Received: by 10.46.71.17 with SMTP id u17mr1919879lja.67.1465021415338; Fri, 03 Jun 2016 23:23:35 -0700 (PDT) Received: from bass.home.chromatix.fi (37-33-56-85.bb.dnainternet.fi. [37.33.56.85]) by smtp.gmail.com with ESMTPSA id h4sm842876lbc.38.2016.06.03.23.23.33 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 03 Jun 2016 23:23:34 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) From: Jonathan Morton In-Reply-To: Date: Sat, 4 Jun 2016 09:23:32 +0300 Cc: Noah Causin , cake@lists.bufferbloat.net, "codel@lists.bufferbloat.net" Content-Transfer-Encoding: quoted-printable Message-Id: <7689BD93-A364-412C-A969-B29116BB3D10@gmail.com> References: <22371476-B45C-4E81-93C0-D39A67639EA0@gmx.de> <857AEE56-E7DB-4981-B32E-82473F877139@gmail.com> <8AB0D25D-C1CA-45F1-889E-2F73CF8C44F7@gmail.com> <323AFC22-A092-4F59-8197-AF21EF73FD58@gmail.com> <274D3A0FA900FD47AA6B56991AAA32FDC5529FC8@wtl-exchp-1.sandvine.com> <574478B4.7080103@taht.net> <39F38477-A877-4C1B-9B7F-BB3358425F17@gmail.com> <0eb223f9-2873-7f53-c2ce-c6867ddec17c@gmail.com> <48A25043-19E2-4BB7-B634-A4003F7BE6F8@gmail.com> To: Andrew McGregor X-Mailer: Apple Mail (2.3124) Subject: Re: [Cake] [Codel] Proposing COBALT 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: Sat, 04 Jun 2016 06:23:37 -0000 > On 4 Jun, 2016, at 04:01, Andrew McGregor = wrote: >=20 > There are undoubtedly DCTCP-like ECN responses widely deployed, since > that is the default behaviour in Windows Server (gated on RTT in some > versions). But also, ECN bleaching exists, as do servers with ECN > response turned off even though they negotiate ECN. It would be good > to know some specifics as to which site, whose DC they're hosted in, > etc. I=E2=80=99m keeping my mouth shut until I=E2=80=99ve analysed the = specific traffic in more detail, so I know what I=E2=80=99m accusing = people of and precisely who to accuse. It=E2=80=99s even possible that = the fault lies in my ISP=E2=80=99s network - I think they=E2=80=99ve = made some significant changes recently. If people are really negotiating ECN and then ignoring its signals at = the host level, that=E2=80=99s a clear RFC violation. Fortunately, I = think this particular site would be interested in correcting such = behaviour if confirmed and explained. > Also, do you have fallback behaviour such that an ECN-unresponsive > flow eventually sees drops? I think that will be essential. Yes, COBALT essentially *is* such a mechanism. The Codel half always = uses ECN if it=E2=80=99s available (and drops otherwise), but the BLUE = half - the part responsible for handling unresponsive flows in the first = place - always uses packet drops. Cake also performs =E2=80=9Chead drop on the longest queue=E2=80=9D when = the global queue limit is reached (as does fq_codel). This can be = considered a second such mechanism, though a much blunter one; it is = significantly superior to tail-drop for two major reasons, but can = easily result in burst loss. It is also this overflow which acts as the up-trigger for BLUE; the = longest queue not only gets the instant head-drop but a notification to = its COBALT instance. - Jonathan Morton