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 1D2A421F18F for ; Tue, 7 Jan 2014 03:35:01 -0800 (PST) Received: from u-081-c096.eap.uni-tuebingen.de ([134.2.81.96]) by mail.gmx.com (mrgmx002) with ESMTPSA (Nemesis) id 0Meg8W-1Vl3VS0APY-00OGqR for ; Tue, 07 Jan 2014 12:34:50 +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: Tue, 7 Jan 2014 12:34:52 +0100 Content-Transfer-Encoding: quoted-printable Message-Id: References: <01558084-B7D8-448A-A4ED-CE36D18AAA97@gmail.com> <52C855B1.1040209@imap.cc> <52CA7CC3.2030203@imap.cc> <52CABC11.6040000@imap.cc> To: David Personette X-Mailer: Apple Mail (2.1510) X-Provags-ID: V03:K0:70ycGJDgVduMMxyyX5vdp4ZXzdCx1GmUopEOxzMssSZQCDUFeIx kvFvzHb1/oNnW23cf1z9ksVp/BFr5heU2G+W+B3Jv437OMTH11vjy8pUATvcuEh9DNaH7vH ucdvEv2WXFuqOE/9KyPqjnpiIDaxsueinOxFzZxEQSrJS/wBc2KtH+B2hD1IpEPXXLSd1bD PHKDAzbTAYDVA3VIOrMtg== Cc: "cerowrt-devel@lists.bufferbloat.net" Subject: Re: [Cerowrt-devel] SQM Question #5: Link Layer Adaptation Overheads 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: Tue, 07 Jan 2014 11:35:09 -0000 X-List-Received-Date: Tue, 07 Jan 2014 11:35:09 -0000 Hi David, On Jan 7, 2014, at 12:08 , David Personette wrote: > I'm in the US, but live in a relatively rural area. My only internet = options are DSL and satellite. The local provider is Century Link (it = used to be Sprint, but they sold their copper phone business off). I = have the fastest service that they offer (based on distance from the = DSLAM), 4 down / .5 up. And you are not alone, a considerable percentage of the = population wherever you look is hanging on such connections. So cerowrt = should really help those folk as well as luckier ones. >=20 > I have had SmokePing monitoring my latency to the first hop outside my = network for over a year now (I've been on CeroWRT the whole time). My = baseline (no load) latency is 31ms. I used to have AQM throttling back = to 80% of my already pathetic bandwidth. I would still regularly see = periods lasting minutes to hours when latency would be 80 - 120ms. >=20 > I only recently grokked what you were talking about with tc_stab since = I got back from the holidays with the family, I set things up as you = suggested for Fred (nfq_codel, "target 25ms" in advanced egress, ATM, = per packet overhead 40, The exact number depends on the encapsulation your ISP uses, 40 = is right for a typical PPPoE over LLC/SNAP connection, if that is = correct for your link you are fine, otherwise contact me if you want to = empirically find out the proper value for your link. > and set my SQM bandwidth limits to 95%). Since the 30th my "worst = case" latency has been 41ms. the fq_codels really are great if in control of the bottleneck, = really good work by bright people!=20 > Plus I get to use more of my actual bandwidth. Well, that I am not so sure. By enabling link layer ATM the = router will automatically take care of the ATM cell overhead for you = (basically reducing the effective rate to ~90% of the link, in other = words you get the same effect by shaping to 90%). It will also handle = the per packet overhead and the nasty potential padding of the last ATM = cell (both have a stronger effect on small packets and are hard to = actually account for by static rate reduction; link layer ATM comes = again to the rescue by taking these two into account individually for = each packet based on the packet size). So effectively 95% with link = layer adjustments might mean a lower wire rate than 80% without; the = important thing is that with the link layer adjustments the link = capacity is estimated correctly avoiding the modem's and the DSLAM's = buffers to fill and cause buffer bloat. > I REALLY wish that I'd made the time to read your emails about setting = up the ATM overhead earlier. Oh, I can understand, when I learned about this some years ago = (by stumbling over Russel Stuart's website and Jesper Brouer's thesis) = it immediate changed my internet experience (I was on a 3 down / 0.5 up = connection at that time). :) Best Regards Sebastian >=20 > Thank you. >=20 > --=20 > David P. >=20 >=20 >=20 > On Mon, Jan 6, 2014 at 9:27 AM, Sebastian Moeller = wrote: > Hi Fred, >=20 >=20 > On Jan 6, 2014, at 15:22 , Fred Stratton wrote: >=20 > > The line rate is 11744/1022 kb/s, but changes moment to moment. SNR = is 12.1 decibel. I am using 11000/950 kb/s as settings. >=20 > So 100 * 11000 / 11744 =3D 93.66% of downlink line rate and = 100* 950 / 1022 =3D 92.95 % of uplink line rate; quite impressive given = the common wisdom of 85% :). >=20 >=20 > > I shall try your suggestion when there is something worth watching = live, to provide a valid comparison, which may not be before 21:30 CET = on Sunday. >=20 > Oh, take your time, this is really not essential, butit would = be a nice data point for figuring out how important the correct overhead = estimate really is in real life, theory being theory and all=85 >=20 > Best Regards > Sebastian >=20 > > > > On 06/01/14 14:12, Sebastian Moeller wrote: > >> Hi Fred, > >> > >> > >> On Jan 6, 2014, at 10:52 , Fred Stratton = wrote: > >> > >>> I have been operating the latest build with 6relayd disabled. The = henet /48 I have been allocated is subnetted correctly, presumably by = dnsmasq. > >>> > >>> I adopted the suggestions to use nfq_codel and an egress target of = 25ms , with an overhead of 40 on a PPPoE connection. I chose to watch = the first 2 episodes of the 3 part third series of 'Sherlock', live on = iPlayer, and these streamed correctly and uninterrupted for 90 minutes. = This was not previously possible. (Quite whether they were up to the = standard of previous episodes is another matter.) > >>> > >>> I can watch iPlayer with little stutter whilst downloading Arch = Linux by torrent, downloading other files at the same time. > >>> > >>> So, for a relatively slow ADSL2+ line, the current build works = well. > >> Out of curiosity, to what percentage of the "current line = rate" (you know the one reported by your modem) you shaped up- and = downlink? And in case you have too much time on your hand, how does the = same feel with an overhead of 10 (to see how bad an overhead = underestimate would feel for a user), since you currently happen to have = a quite sensitive subjective latency evaluation system set up :)=85 > >> > >> Best Regards > >> Sebastian > >> > >>> > >>> On 06/01/14 03:29, Dave Taht wrote: > >>>> On Sat, Jan 4, 2014 at 10:40 AM, Fred Stratton = wrote: > >>>>> Link Names: > >>>>> > >>>>> For consistency, if ADSL is used as a portmanteau term, them = VDSL should be > >>>>> used as the equivalent for VDSL and VDSL2. > >>>>> > >>>>> CeroWRT has to decide whether it is an experimental build, or = something that > >>>>> will eventually be used in production, so these decisions can be = made > >>>>> consistently. > >>>> Well, what I was aiming for was for us to get the sqm scripts and = gui > >>>> up to where they were better than the standard openwrt qos = scripts and > >>>> then push them up to openwrt to where they could be more widely > >>>> deployed. > >>>> > >>>> Aside from being able to dynamically assign priorities in the = gui, we > >>>> are there. Except that nfq_codel is currently getting better = results > >>>> than fq_codel at low bandwidths, and I'm tempted to pour all of > >>>> simple.qos into C. > >>>> > >>>> As for cero's future - certainly since all the snowden = revelations > >>>> I've been going around saying that "friends don't let friends run > >>>> factory firmware". I would like a stable build of sqm and cerowrt = to > >>>> emerge, and to then go off and work on improving wifi. = Regrettably > >>>> what seems to be happening is more backwards than forwards on the > >>>> former, and ramping up on the ath9k and ath10k is taking more = time > >>>> than I'd like, and it seems likely I'll be working on those = primarily > >>>> on another platform and only eventually pushing the results out = to > >>>> cero, mainline kernel > >>>> > >>>> So it's still at the "keep plugging away" point for sqm, ipv6, = cero in > >>>> general, with the stable release always just out of sight. > >>>> > >>>> Tackling the ipv6 problem is next on my agenda on cero, and = getting a > >>>> test suite going is next on my day job. > >>>> > >>>>> I concur with your ADSL setup suggestion as default. I have been = running the > >>>>> Sebastian Moeller ping script overnight to calculate ADSL = overhead for the > >>>>> last several days. After several hours of curve fitting using = Octave, an > >>>>> overhead result is displayed. This novel approach works well. > >>>> It would be nice to get to where we could autoconfigure a router = using > >>>> tools like these with no human intervention. This includes = bandwidth > >>>> estimation. > >>>> > >>>>> The overhead for the particular setup I use was 40 for PPPoE, = and 10 for > >>>>> PPPoA. > >>>>> > >>>>> The default you suggest is a suitable starting point, I suggest. > >>>>> > >>>>> > >>>>> On 04/01/14 18:16, Rich Brown wrote: > >>>>>> QUESTION #5: I still don=92t have any great answers for the = Link Layer > >>>>>> Adaptation overhead descriptions and recommendations. In an = earlier message, > >>>>>> (see > >>>>>> = https://lists.bufferbloat.net/pipermail/cerowrt-devel/2013-December/001914= .html > >>>>>> and following messages), Fred Stratton described the overheads = carried by > >>>>>> various options, and Sebastian Moeller also gave some useful = advice. > >>>>>> > >>>>>> After looking at the options, I despair of giving people a = clear > >>>>>> recommendation that would be optimal for their equipment. = Consequently, I > >>>>>> believe the best we can do is come up with =93good enough=94 = recommendations > >>>>>> that are not wrong, and still give decent performance. > >>>>>> > >>>>>> In this spirit, I have changed Draft #3 of the =93Setting up = SQM=94 page to > >>>>>> reflect this understanding. See > >>>>>> = http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_AQM_for_CeroWr= t_310 > >>>>>> > >>>>>> ADSL/ATM link: Choose =93ADSL/ATM", and set Per Packet = Overhead to > >>>>>> 40 > >>>>>> VDSL2 link: Choose =93VDSL=94, and set Per Packet = Overhead to 8 > >>>>>> Other kind of link (e.g., Cable, Fiber, Ethernet, other = not > >>>>>> listed): Choose =93None (default)=94, and set Per Packet = Overhead to 0 > >>>>>> > >>>>>> NB: I have changed the first menu choice to =93ADSL/ATM=94 and = the second to > >>>>>> =93VDSL=94 in the description. I would ask that we change to = GUI to reflect > >>>>>> those names as well. This makes it far easier/less confusing to = talk about > >>>>>> the options. > >>>>>> > >>>>>> As always, I welcome help in setting out clear recommendations = that work > >>>>>> well for the vast majority of people who try CeroWrt. Thanks. > >>>>>> > >>>>>> Rich > >>>>>> _______________________________________________ > >>>>>> Cerowrt-devel mailing list > >>>>>> Cerowrt-devel@lists.bufferbloat.net > >>>>>> https://lists.bufferbloat.net/listinfo/cerowrt-devel > >>>>> _______________________________________________ > >>>>> Cerowrt-devel mailing list > >>>>> Cerowrt-devel@lists.bufferbloat.net > >>>>> https://lists.bufferbloat.net/listinfo/cerowrt-devel > >>>> > >>> _______________________________________________ > >>> Cerowrt-devel mailing list > >>> Cerowrt-devel@lists.bufferbloat.net > >>> https://lists.bufferbloat.net/listinfo/cerowrt-devel > > >=20 > _______________________________________________ > Cerowrt-devel mailing list > Cerowrt-devel@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/cerowrt-devel >=20