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[83.150.84.172]) by mx.google.com with ESMTPS id e20sm32278943bkv.10.2012.05.14.00.27.59 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 14 May 2012 00:28:00 -0700 (PDT) Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii From: Jonathan Morton In-Reply-To: <1336633359.27520.147.camel@shinybook.infradead.org> Date: Mon, 14 May 2012 10:27:57 +0300 Content-Transfer-Encoding: quoted-printable Message-Id: <326E2D44-7A1E-43B8-A84D-E9A0FF04DD9C@gmail.com> References: <532BA404-30FF-4395-9575-709A68E4C723@gmail.com> <1336631707.27520.136.camel@shinybook.infradead.org> <1336633359.27520.147.camel@shinybook.infradead.org> To: David Woodhouse X-Mailer: Apple Mail (2.1084) Cc: codel@lists.bufferbloat.net, bloat Subject: Re: [Bloat] The challenge 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: Mon, 14 May 2012 07:28:05 -0000 On 10 May, 2012, at 10:02 am, David Woodhouse wrote: > On Thu, 2012-05-10 at 09:54 +0300, Jonathan Morton wrote: >> I want to buy a modem that I can put Linux on, and that supports = ADSL2 >> + Annex M. Where can I get one? >=20 > http://wiki.openwrt.org/doc/hardware/soc/soc.lantiq > http://www.traverse.com.au/productview.php?product_id=3D117 > http://www.traverse.com.au/productview.php?product_id=3D120 >=20 >> Vaguely acceptable solutions include CardBus or PCI/PCIe slot modems >> to put in a PowerBook or a PC.=20 >=20 > http://www.traverse.com.au/productview.php?range_id=3D2 Interesting links, but just as frustrating as usual I'm afraid: 1) A long list of supported devices, without being able to filter for = what's on the shelf in my local superhypermegaretailer, is not helpful. = I looked up the devices I already own, which are a reasonable selection = from said shelf - no dice. I broke open one (a Zyxel P660H-D1) that had = a similar model number to a supported device - but it's totally = different hardware, for which support is only "pending". 2) The Traverse links lead me to two types of devices - one of which is = a router-type box which looks promising, but comes without documentation = (see the next point below for why I want to read that *first*) and is = not listed by *any* of the resellers linked to by the manufacturer - on = any of the three continents listed. So I can't buy it in any obvious = way anyway. (Yes, there is a chap in Belgium who says he will take = requests. I still want to read adequate documentation before imposing = on him.) 3) The second type of device is a PCI card which appears to have the = combination of an Ethernet NIC and a DSL modem *in series* on board. = This has no advantage, to my mind, over a standard consumer box such as = I have several of already - the uplink bottleneck queue is still in a = device that I can't control adequately, and which does not directly = exert back-pressure on the Linux network stack. So I repeat my question: where can I reliably go and buy a DSL modem = that I can put Linux on? It probably helps to mention that I'm in = Finland, so a European (or at least British) reseller is preferable. On the plus side, I did manage to get my PowerBook based router/firewall = working again, so I've put my CPE back into bridge mode and suddenly the = Internet works properly again. Yay. But I still have to manually = configure HTB to match the link rate of the modem if I wan to control = the queue. That's the problem I really want to solve by putting Linux = into the modem itself. So I did some quick subjective tests using HTB/SFQ and HTB/CoDel - I'd = like to try HTB/fq_codel too. No packet classification going on here, = traffic is traffic, let's make our modem devices as dumb as possible, = but no dumber. Bandwidth limits applied both upstream and down - I'm = currently running on a simulated decade-old ADSL1 link at 1M/256K, but I = can and have easily changed that to 128K/128K to simulate ISDN. CoDel seems to cope quite well with everything I throw at it, keeping = the link responsive. However, so does SFQ - at least from a user = perspective. Looking at packet traces, it is immediately clear that SFQ = still allows individual flows to run very unresponsive, with SACK flags = maxed out for many seconds at a time. CoDel achieves similar = responsiveness (SSH remains essentially usable at 128K under multiple = load, which is impressive) but does so by dropping several percent of = all packets. The fact that it is dropping packets rather than ECN-marking them = suggests that I'm still missing something in my network setup, so I need = to figure out what that is. Even so, the flow recovers (by = retransmission) within a dozen packets even over the real Internet, = which is considerably faster than SFQ and gives the application smoother = data delivery once the window size has grown beyond the buffer size. With either CoDel or SFQ on the bottleneck queue, even 1M/256K feels = fast, subjectively. Objectively, I can still observe Steam taking 10x = as long to download a game update than usual, or some YouTube videos no = longer streaming in realtime (because they require 5Mbps for that), but = those are expected. Plain old Web browsing, e-mail, posting on forums = (including reasonably sized photos) and software updating works smoothly = and unobtrusively, even at a tenth of my usual bandwidth in either = direction. At ISDN speeds, a few problems start to appear with applications that = have come to rely on always-on broadband characteristics. Linux Mint = has decided to download megabytes of software catalogue updates every = hour by default, which consumes a large fraction of available bandwidth = - I soon cut that back to every 12 hours. No real problems emerged with = SFQ or CoDel though. Running with just HTB/FIFO, SSH was hilariously = unusable as soon as any load was put on the link in either direction, = but either option solved that almost entirely. I really want to try combining CoDel and SFQ. - Jonathan Morton