From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.17.20]) (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 3546E21F0BD for ; Thu, 13 Mar 2014 02:28:04 -0700 (PDT) Received: from u-089-cab204a2.am1.uni-tuebingen.de ([134.2.89.3]) by mail.gmx.com (mrgmx103) with ESMTPSA (Nemesis) id 0LiDHj-1WtBkQ2qnL-00nSaU; Thu, 13 Mar 2014 10:28:01 +0100 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 6.6 \(1510\)) From: Sebastian Moeller In-Reply-To: Date: Thu, 13 Mar 2014 10:28:02 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: References: To: Andrew McGregor X-Mailer: Apple Mail (2.1510) X-Provags-ID: V03:K0:47/poDX3w8wqc+dP+Cs9MY7/BHrW8vTHGnjZzWA7b+7P4e/9KCo qJgjNUkESw6Tt/9TY30k8xHHXqD5qw4xyzR92a1bdcrSs7wvP8AVCJiQYYnqoC43dk2CxlT Q7U8vWgU5TSk0P91k4DsYrlGSoLedBRd4F9mCx/oYAbepxzJLWM9xhEKLVij7kaejpdtu0i SS9zNsOe3RqFAFTbVC6fA== Cc: codel@lists.bufferbloat.net Subject: Re: [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 09:28:04 -0000 Hi Andrew, On Mar 13, 2014, at 10:04 , Andrew McGregor = wrote: > My intuition suggests something like: > Target =3D 4ms + MTU sized packet duration > Interval =3D target * 20 The current version just does MTU plus overhead packet duration = (basically taking 1544 as maximal DSL packet size, it is not that this = needs to be precise to the last bit) and does interval =3D interval + = target - 5ms, so basically it increases target and interval by the same = amount (note we take the maximum of the calculated argot and 5ms), Where = does your 4ms come from? I wonder whether the important step is increasing the target or = wether it is to change the ratio of interval and target (the current = method basically does both). Thanks for your input best regards Sebastian >=20 > (But only if the resulting interval is more than 100ms) >=20 > Possibly the packet duration may need a small factor (2 or 3) to get = the balance right. >=20 > On 13 Mar 2014 19:41, "Sebastian Moeller" wrote: > Dear Experts, >=20 > 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 >=20 > 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. >=20 >=20 > Bet Regards > Sebastian > _______________________________________________ > Codel mailing list > Codel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/codel