From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-31-ewr.dyndns.com (mxout-055-ewr.mailhop.org [216.146.33.55]) by lists.bufferbloat.net (Postfix) with ESMTP id C20AB2E0188 for ; Wed, 2 Feb 2011 07:20:43 -0800 (PST) Received: from scan-31-ewr.mailhop.org (scan-31-ewr.local [10.0.141.237]) by mail-31-ewr.dyndns.com (Postfix) with ESMTP id 7D03F6FA487 for ; Wed, 2 Feb 2011 15:20:41 +0000 (UTC) X-Spam-Score: 0.1 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 75.145.127.229 Received: from gw.co.teklibre.org (75-145-127-229-Colorado.hfc.comcastbusiness.net [75.145.127.229]) by mail-31-ewr.dyndns.com (Postfix) with ESMTP id 75D126F961D for ; Wed, 2 Feb 2011 15:20:37 +0000 (UTC) Received: from cruithne.co.teklibre.org (unknown [IPv6:2002:4b91:7fe5:2:21c:25ff:fe80:46f9]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "cruithne.co.teklibre.org", Issuer "CA Cert Signing Authority" (verified OK)) by gw.co.teklibre.org (Postfix) with ESMTPS id 357895E839 for ; Wed, 2 Feb 2011 08:20:36 -0700 (MST) Received: by cruithne.co.teklibre.org (Postfix, from userid 1000) id 65C02122143; Wed, 2 Feb 2011 08:20:35 -0700 (MST) From: d@taht.net (Dave =?utf-8?Q?T=C3=A4ht?=) To: bloat Organization: Teklibre - http://www.teklibre.com Date: Wed, 02 Feb 2011 08:20:35 -0700 Message-ID: <87bp2upinw.fsf@cruithne.co.teklibre.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: [Bloat] TCP vegas vs TCP cubic 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: Wed, 02 Feb 2011 15:20:44 -0000 On a suggestion from one of the posters to jg's blog, I took a look at tcp vegas. The results I got were puzzling. With tcp cubic, I typically get 71Mbit/sec and all the side effects of bufferbloat with a single stream. With vegas turned on, a single stream peaks at around 20Mbit. 10 vegas streams did about 55Mbit in total. Can I surmise that TCP cubic is like a dragster, able to go really fast in one direction down a straightaway, and TCP vegas more like an 80s model MR2, maneuverable, but underpowered? The testbed network: http://nex-6.taht.net/images/housenet.png The test path: laptop->nano-m->nano-m->openrd (I note that this path almost never exhibits packet loss) Most of the machines on the path are running with minimal txqueues and dma buffers running as low as they can go. The tests: With cubic: $ openrd: iperf -s $ laptop: iperf -t 60 -c openrd With vegas (on both laptop and server) modprobe tcp_vegas echo vegas > /proc/sys/net/ipv4/tcp_congestion_control openrd:$ iperf -s laptop:$ iperf -t 60 -c openrd & laptop:$ ping On a failed hunch, I also re-ran the tests with a much larger congestion window: echo /proc/sys/net/core/rmem_max echo /proc/sys/net/core/wmem_max iperf -w8m -s To no net difference in effect. -- Dave Taht http://nex-6.taht.net