From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from nm23-vm4.access.bullet.mail.gq1.yahoo.com (nm23-vm4.access.bullet.mail.gq1.yahoo.com [216.39.63.111]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id DA1C921F6B0 for ; Fri, 29 Aug 2014 06:52:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rogers.com; s=s1024; t=1409320352; bh=aNnwIunfo1xKwrrWPRmyHUwGlCRLDROEy7zqu5vFm6A=; h=Received:Received:Received:DKIM-Signature:X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Message-ID:Date:From:Reply-To:User-Agent:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=ZgzgrAIw0BXs8dfwvR7LO9xF5m9NI55iv3qEGtuSs+XM3QRlN+DHbOxNLNQN5Oy5dlkC40Na/mNf9YSOHZvbi4S1O6eiegNwXgHF/9AEPnrZ6xFqR2DfNMFcKNzYROFRAM3Z9p+5j1Crmr5rGNiMYh3RsI7xIX2F7EHCw85wjXU= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=rogers.com; b=eo7QsAf9dFNlzRlp8YRAAyZvpqjuZuNgYtjNyQWd8zM9yMI1cRdLxxuHLsnRgdgUioeLr6OB9tVDpkUPUckXuNkzRmn8gWJ6SeSKeIg/5zciUixWPCkTlPiDLKlW1ZO5HGv02TMnD4Q6ROSO9iqYp+9WVZRnbu6m740q8rnRei0=; Received: from [216.39.60.172] by nm23.access.bullet.mail.gq1.yahoo.com with NNFMP; 29 Aug 2014 13:52:32 -0000 Received: from [67.195.22.116] by tm8.access.bullet.mail.gq1.yahoo.com with NNFMP; 29 Aug 2014 13:52:32 -0000 Received: from [127.0.0.1] by smtp111.sbc.mail.gq1.yahoo.com with NNFMP; 29 Aug 2014 13:52:32 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rogers.com; s=s1024; t=1409320352; bh=aNnwIunfo1xKwrrWPRmyHUwGlCRLDROEy7zqu5vFm6A=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Message-ID:Date:From:Reply-To:User-Agent:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=UIZeivr61B5ohxJud8hrZsFTXonwlc1demkaTtzoyaNYKl6hfceRKHa3wjKs5DlIX5cqER03HkungYw93mfs2+sQltRVELcMZdd2gynMV5DIf2aB6U3gUGBgHqUaqR18D0eHvpwgUPrZvrDj1a00BaipPt27CTIlPWiQxFu+Lco= X-Yahoo-Newman-Id: 67672.94784.bm@smtp111.sbc.mail.gq1.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: qmeRxwkVM1kMSZ8.Y1ujfKXOrN72iw5TE.vsU7swySlcguJ qc301UAXYwqZ2ZfgO1rUMgZ5_f0yXVB_4C0_E3FMZvfb7sV_yAcd8F5HUyjx DV4es_za2RIb.QXGaImtyxzZ3bvg9oRXngVFaJ7eaBYZre1Y5XMwqZbHNjEb GlE50opoX.0hG_KWSFbsFDUMAlz9owBnWeFmrC0j2tw53339FUN3WqRb6vw0 n02n7S12DYJgYoubeZ.EAzd4JEQwqPdGtJQDK4XjJAvfHOFRpjDF.kkZK0ZU l_uJI3aLZUPiwgNGLnvUTkGQfF.nGphleyOQ2SxFYVQEAB0H1Mn6Yjbl9WQl RHXvCLs32Rzpfzcy2bX4peth54.qli2sJGoyt95_2PidBeFOJYAUGw4m8FPT LGmVUqLLZPb39DjESgXrmGeWBR.bOU0AyEwwfU1JTuC.kXsedcobfAayFrkq 54filSFlT8R1nAHd.Jvu2evONLN6b92nR1REsgl9SadELbZ0kQiq5CS0s_pS jvFSI66qjtGSbS4TMX7T981x2JoWmiASiLg-- X-Yahoo-SMTP: sltvjZWswBCRD.ElTuB1l9j6s9wRYPpuyTNWOE5oEg-- Message-ID: <5400859E.6070202@rogers.com> Date: Fri, 29 Aug 2014 09:52:30 -0400 From: David Collier-Brown User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: aqm@ietf.org References: <53E8D7B0.9040007@mti-systems.com> <20140811233857.GL45982@verdi> <201408120943.s7C9hRvV024419@bagheera.jungle.bt.co.uk> <53E9EB49.9040509@erg.abdn.ac.uk> <16141ccda1c843ab8f03fb5f478db010@hioexcmbx05-prd.hq.netapp.com> In-Reply-To: <16141ccda1c843ab8f03fb5f478db010@hioexcmbx05-prd.hq.netapp.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: bloat Subject: Re: [Bloat] [aqm] adoption call: draft-welzl-ecn-benefits X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list Reply-To: davecb@spamcop.net List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 29 Aug 2014 13:52:33 -0000 On 08/29/2014 09:16 AM, Scheffenegger, Richard wrote: > Hi Gorry, > >>> Given QUIC includes FEC to hide losses, I guess it is a good example to >>> consider whether ECN still offers sufficient benefits over and above >>> just removing losses. >>> >> GF: And then, isn't the implication of AQM to significantly increase the >> number of "losses" unless we use ECN? >> >> Indeed, I have the impression we are confusing many on these points - >> ECN could change the reaction to congestion signal, and FEC (even >> opportunistic CC-friendly FEC) can also change the way things react to >> congestion signals. > I don't think that an AQM's implication is automatically to increase the number of losses; that may happen to specific flows (in particular, unresponsive ones), but for responsive (non-ECN) ones, the expectation would be to de-correlate the losses, and for TCP, to only have around 1 loss per window when necessary - instead of a burst loss of one window and the expensive recovery... > > Perhaps it's that perception that also poses an obstacle to AQM deployment, because of the believe that a dynamic but lower mark/drop threshold will cause more losses? Goodness gracious, from the point of view of a queuing network, AQM reduces losses overall, in the process of minimizing delay and keeping bandwidth use just below the theoretical maximum. Oversimplifying, we try to keep the buffers empty, so that if we get a burst we can handle it without losses and without affecting other communications. We signal via a loss or other indicator if the non-bursty flow is enough to cause congestion, which keeps the buffers near-empty and the system uncongested. Failing to do so fills the buffers without signalling there is congestion, and induces delay on everyone who's dependant on the buffer. Not to mention allowing the congestion to go unreported! It's not a tradeoff discussion: it's arguably one about correctness. --dave [Somebody like Neil Gunther could explain the math of this better, but the behaviour is well-known in the trade, and cordially hated. Congestion control is superior to admission control, which is what I often use to prevent the server equivalent of congestive collapse (:-))] -- David Collier-Brown, | Always do right. This will gratify System Programmer and Author | some people and astonish the rest davecb@spamcop.net | -- Mark Twain