From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qw0-f43.google.com (mail-qw0-f43.google.com [209.85.216.43]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id BF92720014B for ; Thu, 26 Jan 2012 12:05:00 -0800 (PST) Received: by qabg1 with SMTP id g1so292146qab.16 for ; Thu, 26 Jan 2012 12:04:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=sender:message-id:date:from:organization:user-agent:mime-version:to :subject:content-type:content-transfer-encoding; bh=1xCSPYtLKOGHlLOI6YiNoJPvNlQFoBWUfFHwn02NeM4=; b=SbN9f9to/RTj/ncH1ocwvwJg6/qXoiO3ozPRnAp+cEz147JiewOGwD7S+O/ba3jtU3 qlIbDySj7j2wCP3Ww70UvmdRzy5pLxDP1sUbGOdcJ0ThDBwZkRHaAqADDN+gRueDJjGU w2Q7dEmCcf5yVkb3anD/bBI/yACEcksGlySXY= Received: by 10.224.173.146 with SMTP id p18mr4795048qaz.8.1327608299378; Thu, 26 Jan 2012 12:04:59 -0800 (PST) Received: from [192.168.1.27] (c-24-63-191-17.hsd1.ma.comcast.net. [24.63.191.17]) by mx.google.com with ESMTPS id dk2sm10264380qab.12.2012.01.26.12.04.57 (version=SSLv3 cipher=OTHER); Thu, 26 Jan 2012 12:04:58 -0800 (PST) Sender: Jim Gettys Message-ID: <4F21B1E8.9010504@freedesktop.org> Date: Thu, 26 Jan 2012 15:04:56 -0500 From: Jim Gettys Organization: Bell Labs User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111229 Thunderbird/9.0 MIME-Version: 1.0 To: bloat Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: [Bloat] Traffic patterns for AQM testing.... Bursty behaviour of video players. 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: Thu, 26 Jan 2012 20:05:01 -0000 Since we're rapidly getting to the point of needing to test AQM algorithms (as enough of the underbrush has been cleared away), I've been thinking a bit about how to test the algorithms. I've been inspired to think a bit about whether, given both the changes in web browsers and the advent of "streaming" media to add to the classic full speed "elephant" flow, what a test scenario for both simulation and actual tests should look like. I feel I have some idea of how HTTP works and web browsers given my experience of the 1990's; if people have any real data (taken from the edge please!) I'd like to update my knowledge; but it's going to be bursty, and due to using so many connections, most of those packets will not be under congestion avoidance (would that SPDY and HTTP/1.1 pipelining get deployed quickly...) And classic elephant flows we know... I finally thought today to just use CeroWrt/OpenWrt's nice traffic plotting stuff to get a feel for a number of video players's behaviour (I happened to use an iPad; I sampled Netflix, Hulu, and IMDB). As I expected, there is a large amount of data transferred as fast as possible at the beginning, to try to hide performance problems (much of which are being caused by bufferbloat, of course). These will clearly drive latencies well up. What's interesting is what happens after that: rather than, having had a period to observe how fast they are able to transfer data, both Netfix and Hulu appear to actually "burst" their later transfers. The data is not "streamed" at all, rather it is sent in full rate bursts approximately every 10 seconds thereafter. (which will induce bursts of latency). IMDB seems to buffer yet more than Netfix and Hulu (watching HD movie clips); I should experiment a bit more with it. The interesting question is what do current operating systems/standards do to the TCP window when idle? Anyone know? I'm making a (possibly poor) presumption that they are using single TCP connections; I should probably take some traces.... - Jim