From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-14-iad.dyndns.com (mxout-105-iad.mailhop.org [216.146.32.105]) by lists.bufferbloat.net (Postfix) with ESMTP id 793E72E00B9 for ; Thu, 17 Mar 2011 14:50:06 -0700 (PDT) Received: from scan-12-iad.mailhop.org (scan-12-iad.local [10.150.0.209]) by mail-14-iad.dyndns.com (Postfix) with ESMTP id 8699644A70E for ; Thu, 17 Mar 2011 21:50:05 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 74.125.82.171 Received: from mail-wy0-f171.google.com (mail-wy0-f171.google.com [74.125.82.171]) by mail-14-iad.dyndns.com (Postfix) with ESMTP id 2AA9744A700 for ; Thu, 17 Mar 2011 21:50:05 +0000 (UTC) Received: by wyb32 with SMTP id 32so3905550wyb.16 for ; Thu, 17 Mar 2011 14:50:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to:x-mailer; bh=uHV5dkX7DdaGWkDpepR2cI2ga3AsJluMyIW/rs6lVyI=; b=bLbkEb/282SvWw5gUQ9w8zHNE2GKF5c6wRDTDHe6SmUolDD00EkDdBbpcvp6t6L5dT 0dkuQhW8kFB9An2kkMX7q8YXq5yDWx0zEP1qh5O5VDOjF6GVki9HwXS/nB0DM7leGli6 Ilw3+gqqMfRiHq68eXFrZE8i9AmRah24DwbFU= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer; b=EtasQBmSGf15f0mU6SVNUruhTPeRgcOPJlnuK5U0gsJmtvU07ReY+ADvLXaOaKVdgf OLU1fsTGwczFM9e1U9rPJX4mrsxtR0HzLTPyojmLV/R9A88zzAiL1spwSnbAY1reBqvb 2oMLZpV/wrYqwDzE2YHxLwV5s8YVomu87N5q4= Received: by 10.216.246.5 with SMTP id p5mr38132wer.64.1300398604576; Thu, 17 Mar 2011 14:50:04 -0700 (PDT) Received: from [192.168.239.42] (xdsl-83-150-84-172.nebulazone.fi [83.150.84.172]) by mx.google.com with ESMTPS id n2sm1296137wej.46.2011.03.17.14.50.03 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 17 Mar 2011 14:50:04 -0700 (PDT) Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=us-ascii From: Jonathan Morton In-Reply-To: <1300386132.2087.2345.camel@tardy> Date: Thu, 17 Mar 2011 23:50:02 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <44F5E713-4AB2-4D34-9DD5-97FBE92E401F@gmail.com> References: <4D7F4121.40307@freedesktop.org> <20110315175942.GA10064@goldfish> <1300212877.2087.2155.camel@tardy> <20110315183111.GB2542@tuxdriver.com> <29B06777-CC5F-4802-8727-B04F58CDA9E3@gmail.com> <20110315205146.GF2542@tuxdriver.com> <219C7840-ED79-49EA-929D-96C5A6200401@gmail.com> <20110316004722.GD28663@tuxdriver.com> <66469263-763A-4D5A-B689-026D0603C170@gmail.com> <1300386132.2087.2345.camel@tardy> To: rick.jones2@hp.com X-Mailer: Apple Mail (2.1082) Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps? 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: Thu, 17 Mar 2011 21:50:06 -0000 On 17 Mar, 2011, at 8:22 pm, Rick Jones wrote: >> For the benefit of the 3G folks, here are some helpful axioms to = discuss: >>=20 >> 1) Buffering more than a couple of seconds of data (without employing >> AQM) is unhelpful, and will actually increase network load without >> increasing goodput. Unless there is a compelling reason, you should >> try to buffer less than a second. >>=20 >> This is because congestion and packet-loss information takes longer = to >> influence existing flows, and new flows are more difficult to start.=20= >> After about 3 seconds of no information, most TCPs will start >> retransmission - regardless of whether the packets were physically >> lost, or are simply languishing in a multi-megabyte buffer somewhere. >=20 > So initialRTO is specced currently to be 3 seconds, with a small but > non-trivial effort under way to reduce that, but once established > connections have a minimum RTO of less than or equal to a second don't > they? If the RTT they measure is low enough, then yes. If the queues = lengthen, the measured RTT goes up and so does the RTO, once the = connection is established. But the *initial* RTO is the important one for unmanaged queue sizing, = because that determines whether a new connection can be started without = retransmissions, all else functioning correctly of course. There is no = way to auto-tune that. Note also that with AQM that can re-order packets, the length of the = bulk queue starts to matter much less, because the SYN/ACK packets can = bypass most of the traffic. In that case the RTT measured by the = existing bulk flows will be higher than the latency seen by new and = interactive flows. - Jonathan