From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-12-ewr.dyndns.com (mxout-083-ewr.mailhop.org [216.146.33.83]) by lists.bufferbloat.net (Postfix) with ESMTP id 246F62E044B for ; Fri, 4 Feb 2011 05:56:59 -0800 (PST) Received: from scan-11-ewr.mailhop.org (scan-11-ewr.local [10.0.141.229]) by mail-12-ewr.dyndns.com (Postfix) with ESMTP id 8BD5A930905 for ; Fri, 4 Feb 2011 13:56:56 +0000 (UTC) X-Spam-Score: 0.0 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 76.96.62.64 Received: from qmta07.westchester.pa.mail.comcast.net (qmta07.westchester.pa.mail.comcast.net [76.96.62.64]) by mail-12-ewr.dyndns.com (Postfix) with ESMTP id 35BB8930856 for ; Fri, 4 Feb 2011 13:56:53 +0000 (UTC) Received: from omta20.westchester.pa.mail.comcast.net ([76.96.62.71]) by qmta07.westchester.pa.mail.comcast.net with comcast id 3pVX1g0011YDfWL57pwu20; Fri, 04 Feb 2011 13:56:54 +0000 Received: from [192.168.1.119] ([98.229.99.32]) by omta20.westchester.pa.mail.comcast.net with comcast id 3pws1g0140hvpMe3gpwtml; Fri, 04 Feb 2011 13:56:53 +0000 Message-ID: <4D4C05A3.3000901@freedesktop.org> Date: Fri, 04 Feb 2011 08:56:51 -0500 From: Jim Gettys Organization: Bell Labs User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101208 Lightning/1.0b2 Thunderbird/3.1.7 MIME-Version: 1.0 To: bloat@lists.bufferbloat.net References: <87k4hgdte9.fsf@trurl.pps.jussieu.fr> In-Reply-To: <87k4hgdte9.fsf@trurl.pps.jussieu.fr> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Bloat] About Stochastic Fair Blue (SFB) X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Feb 2011 13:57:00 -0000 On 02/04/2011 04:46 AM, Juliusz Chroboczek wrote: > Hi again, > > In his series of articles, Jim has concentrated on router-based > solutions to delay issues. He mentioned AQM policies in routers, and > notably the venerable RED. Referred to hereafter as RED 93. For those of you who have not waded through all the postings, RED is often all that has been available in most Internet routers, and RED 93 won't handle the common case we face most commonly, which is 802.11. (This is the opinion of Van Jacobson, who with Sally Floyd invented RED 93). The reasons for this is that RED 93 can't handle the highly variable "goodput" we see in wireless networks (and some other systems) due to its static configuration, and Van says it's stability given the volatile traffic mix we have in these networks also makes RED 93 hopeless. I just want to make clear we face a problem here we can't solve with RED 93. We have to explore our alternatives in detail. > > AQMs are designed to achieve two different (but not necessarily > contradictory) goals: to improve the behaviour of the traffic (notably > by reducing the amount of buffering, which is what we're concerned about > here), and to improve fairness. For example, RED is mostly concerned > with the former, while CHOKe is only concerned with the latter. If we don't manage these insane buffers, we've lost. > > One AQM that attempts both is Stochastic Fair a stochastically-fair > variant of BLUE [1]. In addition to reducing buffer size and enforcing > rough inter-flow fairness, SFB will reliably detect unresponsive flows > and rate-limit them. > > In order to experiment with SFB, I've implemented it for Linux a couple > of years ago [2]. Unfortunately, I've given up for now on trying to get > it into the mainline kernel, and I'm not sure I want to try again [3]. > > --Juliusz > > [1] W. Feng, D. Kandlur, D. Saha, K. Shin. Blue: A New Class of Active > Queue Management Algorithms. U. Michigan CSE-TR-387-99, April 1999. > http://www.thefengs.com/wuchang/blue/CSE-TR-387-99.pdf > [2] http://www.pps.jussieu.fr/~jch/software/sfb/ > [3] http://article.gmane.org/gmane.linux.network/183813 Juliusz, have you thought about the host case at all? One of the places we're getting insane buffering is in the operating systems themselves (e.g. the experiment I did with a 100Mbps switch). My intuition is that we have to do AQM in hosts, not just routers. - Jim