From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-33-ewr.dyndns.com (mxout-120-ewr.mailhop.org [216.146.33.120]) by lists.bufferbloat.net (Postfix) with ESMTP id 0C2322E0132 for ; Thu, 7 Apr 2011 12:26:18 -0700 (PDT) Received: from scan-32-ewr.mailhop.org (scan-32-ewr.local [10.0.141.238]) by mail-33-ewr.dyndns.com (Postfix) with ESMTP id 1A3FF6FEEDA for ; Thu, 7 Apr 2011 19:26:18 +0000 (UTC) X-Spam-Score: 0.0 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 149.20.54.64 Received: from mainmail.teklibre.com (toutatis.isc.org [149.20.54.64]) by mail-33-ewr.dyndns.com (Postfix) with ESMTP id 53A1E6FEE8D for ; Thu, 7 Apr 2011 19:26:10 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mainmail.teklibre.com (Postfix) with ESMTP id 0821712B752; Thu, 7 Apr 2011 13:00:05 -0700 (PDT) Received: from mainmail.teklibre.com ([127.0.0.1]) by localhost (toutatis.sql1.isc.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Msmyjlot-X2B; Thu, 7 Apr 2011 13:00:04 -0700 (PDT) Received: from [143.215.105.6] (lawn-143-215-105-6.lawn.gatech.edu [143.215.105.6]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: d) by mainmail.teklibre.com (Postfix) with ESMTPSA id 766FC12B6AB; Thu, 7 Apr 2011 13:00:04 -0700 (PDT) Message-ID: <4D9E0FCF.9090701@taht.net> Date: Thu, 07 Apr 2011 13:26:07 -0600 From: Dave Taht User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.14) Gecko/20110223 Thunderbird/3.1.8 MIME-Version: 1.0 To: bismark-devel@lists.bufferbloat.net, jg@freedesktop.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Bismark-devel] How to measure the initial TCP impulse generated by a web browser? X-BeenThere: bismark-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Apr 2011 19:26:19 -0000 Jim has been worrying about the size of the initial impulse being generated by the increase in the initial windows across multiple operating systems from 4 to 10 or more, and how to look at that brief, transient impulse, and later, its effect on TCP window scaling. He messaged me earlier today with: The best thing I've been able to think is to get a packet capture, having triggered a bunch of simultaneous HTTP get's on a web server. Current browsers are doing 6 over the same path (and FF may do 15 under some circumstances). If you have a sharded web site, you can get yet more packets in flight, as the web browser doesn't know it's actually the same web site. On sites like google images, the connections may be persistent, and the window size may be growing further when you scroll to the next page. Dunno. Here's a rough computation # connections IW Size of "splat" Comments 2 4 8 packets RFC 2068/2616 behaviour 6 4 24 Packets Current browser + old IW 6 10 60 packets Current browser + new IW proposal Not pretty. Then from timestamp data (even best if it is TCP timestamp data), one should be able to figure out how long a broadband link is saturated by the packet burst that arrives.