From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-out4.uio.no (mail-out4.uio.no [IPv6:2001:700:100:10::15]) (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 E170921F3DE; Fri, 20 Mar 2015 13:59:45 -0700 (PDT) Received: from mail-mx6.uio.no ([129.240.10.40]) by mail-out4.uio.no with esmtp (Exim 4.80.1) (envelope-from ) id 1YZ417-0006gH-5d; Fri, 20 Mar 2015 21:59:41 +0100 Received: from 173.179.249.62.customer.cdi.no ([62.249.179.173] helo=[192.168.0.114]) by mail-mx6.uio.no with esmtpsa (TLSv1:DHE-RSA-AES256-SHA:256) user michawe (Exim 4.80.1) (envelope-from ) id 1YZ416-0002Pr-GP; Fri, 20 Mar 2015 21:59:41 +0100 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2070.6\)) From: Michael Welzl In-Reply-To: <2E2D6622-1791-4CBB-856E-CE7BA39D99E0@gmail.com> Date: Fri, 20 Mar 2015 21:59:37 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: <4C566C48-769A-4AC9-910F-B852EBF4B7A8@ifi.uio.no> References: <20150316203532.05BD21E2@taggart.lackof.org> <123130.1426635142@turing-police.cc.vt.edu> <15A0911A-E3B7-440A-A26B-C5E1489EA98B@viagenie.ca> <1426773234.362612992@apps.rackspace.com> <2E2D6622-1791-4CBB-856E-CE7BA39D99E0@gmail.com> To: Jonathan Morton X-Mailer: Apple Mail (2.2070.6) X-UiO-SPF-Received: X-UiO-Ratelimit-Test: rcpts/h 5 msgs/h 1 sum rcpts/h 8 sum msgs/h 2 total rcpts 26665 max rcpts/h 44 ratelimit 0 X-UiO-Spam-info: not spam, SpamAssassin (score=-5.0, required=5.0, autolearn=disabled, TVD_RCVD_IP=0.001, UIO_MAIL_IS_INTERNAL=-5, uiobl=NO, uiouri=NO) X-UiO-Scanned: AA1795EAAA76464D24D72AAE1C13F688DF19443B X-UiO-SPAM-Test: remote_host: 62.249.179.173 spam_score: -49 maxlevel 80 minaction 2 bait 0 mail/h: 1 total 460 max/h 13 blacklist 0 greylist 0 ratelimit 0 Cc: "Livingood, Jason" , "cerowrt-devel@lists.bufferbloat.net" , bloat Subject: Re: [Cerowrt-devel] [Bloat] DOCSIS 3+ recommendation? X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 Mar 2015 21:00:14 -0000 > On 20. mar. 2015, at 17.31, Jonathan Morton = wrote: >=20 >=20 >> On 20 Mar, 2015, at 16:54, Michael Welzl wrote: >>=20 >> I'd like people to understand that packet loss often also comes with = delay - for having to retransmit. >=20 > Or, turning it upside down, it=E2=80=99s always a win to drop packets = (in the service of signalling congestion) if the induced delay exceeds = the inherent RTT. Actually, no: as I said, the delay caused by a dropped packet can be = more than 1 RTT - even much more under some circumstances. Consider this = quote from the intro of = https://tools.ietf.org/html/draft-dukkipati-tcpm-tcp-loss-probe-01 : *** To get a sense of just how long the RTOs are in relation to connection RTTs, following is the distribution of RTO/RTT values on Google Web servers. [percentile, RTO/RTT]: [50th percentile, 4.3]; [75th percentile, 11.3]; [90th percentile, 28.9]; [95th percentile, 53.9]; [99th percentile, 214]. *** That would be for the unfortunate case where you drop a packet at the = end of a burst and you don't have TLP or anything, and only an RTO = helps... Cheers, Michael