From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.gmx.net (mout.gmx.net [212.227.15.19]) by huchra.bufferbloat.net (Postfix) with ESMTP id A1E66200666 for ; Sat, 9 Feb 2013 11:10:27 -0800 (PST) Received: from mailout-eu.gmx.com ([10.1.101.212]) by mrigmx.server.lan (mrigmx002) with ESMTP (Nemesis) id 0M9cyP-1UDtef2IGN-00D27E for ; Sat, 09 Feb 2013 20:10:26 +0100 Received: (qmail invoked by alias); 09 Feb 2013 19:10:26 -0000 Received: from 75-142-61-179.static.mtpk.ca.charter.com (EHLO hms-beagle.home.lan) [75.142.61.179] by mail.gmx.com (mp-eu012) with SMTP; 09 Feb 2013 20:10:26 +0100 X-Authenticated: #24211782 X-Provags-ID: V01U2FsdGVkX195hKUW6aJ5TMFJTB2UlgJsoevEynJz+riNUW9gS1 2xfVikHIN1DFG4 Mime-Version: 1.0 (Apple Message framework v1283) Content-Type: text/plain; charset=windows-1252 From: this_is_not_my_name nor_is_this In-Reply-To: Date: Sat, 9 Feb 2013 11:10:23 -0800 Content-Transfer-Encoding: quoted-printable Message-Id: References: To: Jonathan Morton X-Mailer: Apple Mail (2.1283) X-Y-GMX-Trusted: 0 Cc: bloat Subject: Re: [Bloat] I am unable to pinpoint the source of bufferbloat 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: Sat, 09 Feb 2013 19:10:28 -0000 Hi Jonathan, On Feb 9, 2013, at 10:15 , Jonathan Morton wrote: > Latency caused by bufferbloat always appears at the bottleneck device. = Usually that is the modem, and you've given no alternative that it could = plausibly be. The modems you mention are slightly different model = numbers, but that can hide substantial differences in internal = configuration. >=20 > For a typical drop-tail queue, the induced latency under load is the = size of the buffer divided by the speed of the link draining it. = Assuming both modems have a 4Mbit uplink, 550ms is consistent with a = 256KB buffer, and 220ms is consistent with a 48KB buffer - neither of = which would seem excessively large to a modem builder who hasn't heard = of bufferbloat. However with a shared cable infrastructure, it is = possible that the uplink is constrained by other users on the same = segment, which will skew this calculation. >=20 > To cure it without modifying the modem, you need to move the = bottleneck to a point where you can control the buffer. You do this by = introducing traffic shaping at slightly below the advertised modem = uplink speed on one of your own machines and directing all upstream = traffic through it. This is great advise, I just want to mention that both openWRT's = QOS settings as well as cerowrt's simple_qos.sh still show some = buffering in netalyzr (in my case accidentally 550ms on the uplink with = a 4000Kbit/s cable connection shaped down to 3880Kbit/s using cerowrt's = (3.7.4-3) simple_qos script). But real measurements with real TCP = traffic (opening 60 webpages simultaneously while saturating the uplink = with a big upload) showed that ping times are only marginally affected = by the cable connection running constantly close to full saturation. My = point netalyzr's worst case scenario is quite a bit detached from real = world performance, and good queue management (using one of the codel = derivates) will give excellent real world performance while still = showing excessive buffering in netalyzr. Make what you will out of that=85= (my not-even-started-yet pet project is to separate tcp from udp = traffic (or even better responsive/elastic from unresponsive/inesastic = traffic)) and treat both to an according dropping strategy, i.e. drop = UDP much harder, but given my time constraints that will happen in the = next decade=85. best Sebastian >=20 > - Jonathan Morton > On Feb 9, 2013 7:27 PM, "Forums1000" wrote: > Hi Jonathan and Dave >=20 > My entire LAN-network is gigabit. My cable subscription is 60 megabit = down and 4 megabit up.=20 > Now, both my routers' WAN-port and the cable modems' LAN port are also = gigabit. The router can route LAN to WAN and the other way around (with = NAT and connection tracking enabled) in excess of 100 megabit.=20 >=20 > Now my cable modem is a Motorola Surfboard SV6120E and hers is a = Motorola Surfboard CV6181E. My upload lag is 550ms and hers is only = 220ms. Moreover, at her place there are Powerplugs in the path limiting = her download to 30 megabit instead of 60 megabit. Yet, the upload lag is = much lower than mine. There, it also did not matter where I ran = Natalyzr, the result was always 220ms of bufferbload. >=20 > Could this still be only the modem? >=20 >=20 > On Sat, Feb 9, 2013 at 10:52 AM, Forums1000 = wrote: > Hi everyone, >=20 > Can anyone give some tips on how to diagnose the sources of = bufferbloat? According to the Netalyzr test at = http://netalyzr.icsi.berkeley.edu/, I have 550ms of upload bufferbloat. = I tried all kinds of stuff on my Windows 7 laptop: >=20 > - For the Intel(R) 82567LF Gigabit Network Connection, I put receive = and transmit buffers to the lowest value of 80 (80 bytes? 80 packets? I = don't know). I also disabled interrupt moderation.=20 > Result? Still 550ms. > - Then I connected my laptop directly to my cable modem, bypassing my = Mikrotik 450G router. Result? Still 550ms of bufferbloat.=20 > - Then I put a 100 megabit switch between the cable modem an the = laptop (as both cable modem and Intel NIC are gigabit). Result? Still = 550ms of upload bufferbloat. >=20 > I'm out of ideas now. It seems I can't do anything at all to lower = bufferbloat. Or the Netalyzr test is broken?:-) >=20 > many thanks for your advice, > Jeroen >=20 >=20 >=20 > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat >=20 > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat