From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-34-ewr.dyndns.com (mxout-053-ewr.mailhop.org [216.146.33.53]) by lists.bufferbloat.net (Postfix) with ESMTP id 5C2362E037A for ; Wed, 13 Apr 2011 04:19:29 -0700 (PDT) Received: from scan-32-ewr.mailhop.org (scan-32-ewr.local [10.0.141.238]) by mail-34-ewr.dyndns.com (Postfix) with ESMTP id A4A0B70BE88 for ; Wed, 13 Apr 2011 11:19:28 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 217.32.164.137 Received: from smtp1.smtp.bt.com (smtp1.smtp.bt.com [217.32.164.137]) by mail-34-ewr.dyndns.com (Postfix) with ESMTP id 612AA70A80C for ; Wed, 13 Apr 2011 11:19:21 +0000 (UTC) Received: from i2kc08-ukbr.domain1.systemhost.net ([193.113.197.71]) by smtp1.smtp.bt.com with Microsoft SMTPSVC(6.0.3790.4675); Wed, 13 Apr 2011 12:19:20 +0100 Received: from cbibipnt08.iuser.iroot.adidom.com ([147.149.100.81]) by i2kc08-ukbr.domain1.systemhost.net with Microsoft SMTPSVC(6.0.3790.4675); Wed, 13 Apr 2011 12:19:20 +0100 Received: From bagheera.jungle.bt.co.uk ([132.146.168.158]) by cbibipnt08.iuser.iroot.adidom.com (WebShield SMTP v4.5 MR1a P0803.399); id 1302693559659; Wed, 13 Apr 2011 12:19:19 +0100 Received: from MUT.jungle.bt.co.uk ([10.73.96.194]) by bagheera.jungle.bt.co.uk (8.13.5/8.12.8) with ESMTP id p3DBJIBu025003 for ; Wed, 13 Apr 2011 12:19:18 +0100 Message-Id: <201104131119.p3DBJIBu025003@bagheera.jungle.bt.co.uk> X-Mailer: QUALCOMM Windows Eudora Version 7.1.0.9 Date: Wed, 13 Apr 2011 12:19:16 +0100 To: From: Bob Briscoe Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed X-Spam-Score: -1.36 () ALL_TRUSTED X-Scanned-By: MIMEDefang 2.56 on 132.146.168.158 X-OriginalArrivalTime: 13 Apr 2011 11:19:20.0485 (UTC) FILETIME=[A27BAD50:01CBF9CC] Subject: [Bloat] queuebloat 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: Wed, 13 Apr 2011 11:19:29 -0000 Folks, [This is to repeat to the list one of many conversations I had with Jim Gettys at the recent IETF...] The term bufferbloat seemed to hit a rich vein in marketing the importance of this problem . But actually it's a misleading name that will confuse (unsavvy) equipment vendors when they come to work out what to do about it. The problem is actually queuebloat, not bufferbloat. The buffer is the memory set aside for the queue. The queue is how much of the memory is used to store packets or frames. We don't want vendors to (necessarily*) reduce the size of the buffer, we want them to reduce the size of the standing queue. They can do that with active queue management (AQM) (if we only knew how to code it robustly). Ideally with ECN too, but AQM would be a good start. A reasonable* sized buffer is still needed to absorb bursts without loss. If builders of kit make their buffers smaller in response to our criticism, during bursts users will experience loss rather than delay. That will lead transports to wait for a timeout to detect these losses. So small buffers would just introduce a new cause of poor responsiveness. The focus should be on small queues, not small buffers. OK, maybe it's not a good idea to ditch a catch-phrase that has captured the public imagination. But we should be careful to nuance its meaning when explaining to kit builders what they should do about it. Cheers Bob ___________ * You don't need buffers larger than the timeouts in typical transport protocols, otherwise a burst can build up more delay than a transport is prepared to wait for. Then you start wasting energy maintaining unnecessary amounts of fast memory. ________________________________________________________________ Bob Briscoe, BT Innovate & Design