From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.18]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (Client CN "mout.gmx.net", Issuer "TeleSec ServerPass DE-1" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 0642121F0BD for ; Thu, 13 Mar 2014 01:41:37 -0700 (PDT) Received: from u-089-cab204a2.am1.uni-tuebingen.de ([134.2.89.3]) by mail.gmx.com (mrgmx001) with ESMTPSA (Nemesis) id 0M6BKc-1XM2ZZ08BG-00yBwK for ; Thu, 13 Mar 2014 09:41:35 +0100 From: Sebastian Moeller Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Message-Id: Date: Thu, 13 Mar 2014 09:41:35 +0100 To: "codel@lists.bufferbloat.net" Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\)) X-Mailer: Apple Mail (2.1510) X-Provags-ID: V03:K0:O2JIeuXpYXiZ1kpX3QTq7dHKN7IYMDBe46Ccn0rjANlipTbPmhm TzKQu7WJUi+ANjNVt06lSLIGOUpBmlyF7LSfJj+zdoM8PHKKY3EKv1WGZXVVBiRbr+40yu1 Ski1zi0Xej8vIYHXGhogmXa2wpne2dF29tqcJKUXAW5Z9QTC3IjJMjh3ZuPbMHhJ0eQI8u8 HDB7grjrSoegqNrMAj2ag== Subject: [Codel] interval target relation ship question X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Mar 2014 08:41:38 -0000 Dear Experts, Codel and especially fq_codel have massively improved = snappiness/interactivity of typical residential internet connections, as = shown in the cerowrt testbed and also in the french ISP free's roll-out = of coddled xddl modems. One observation has been that at low bandwidth = the latency/bandwidth trade-off does not seem to be ideal and an = empirical solution to this problem has been to increase the target as a = function of the available bandwidth. I realize that codel tries to = accommodate for low-bandwidth links by always allowing at least one = packet in the queue. But empirically that does not seem to be enough for = good behavior on slow links (I think the issue is that the bandwidth = sacrifice seems a bit to large)=85 Currently we try to model what we know about free's approach in = cerowrt, basically we increase target as a function of bandwidth and = also increase interval be the same amount as target. Now having read = section "3.2 Setpoint" of = https://datatracker.ietf.org/doc/draft-nichols-tsvwg-codel/?include_text=3D= 1 makes a strong point that target should be in the range of 5-10% of = interval. So would it make more sense to increase interval so that after = adjustments new_target =3D 0.05*new_interval still stays true? Or would = you recommend to do something along the lines of: new_interval =3D 100ms + known DSL link latency (can be in the = range of dozens of ms) new_target =3D new_interval * 0.05 or new_interval * 0.1 I guess I will try to actually test the different approaches in the near = future, but would be delighted to get help establishing a decent = hypothesis before hand which modification actually will work best. Bet Regards Sebastian=