From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-24-ewr.dyndns.com (mxout-024-ewr.mailhop.org [216.146.33.24]) by lists.bufferbloat.net (Postfix) with ESMTP id F34A02E03C0 for ; Thu, 14 Apr 2011 17:09:47 -0700 (PDT) Received: from scan-21-ewr.mailhop.org (scan-21-ewr.local [10.0.141.243]) by mail-24-ewr.dyndns.com (Postfix) with ESMTP id 82C5A5CEEDC for ; Thu, 14 Apr 2011 04:44:54 +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-24-ewr.dyndns.com (Postfix) with ESMTP id 208E65CE6E2 for ; Thu, 14 Apr 2011 04:44:50 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mainmail.teklibre.com (Postfix) with ESMTP id 823423DA121; Wed, 13 Apr 2011 22:19:07 -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 V-U0aNRbjFKH; Wed, 13 Apr 2011 22:19:07 -0700 (PDT) Received: from [172.16.87.195] (c-68-81-97-191.hsd1.pa.comcast.net [68.81.97.191]) (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 CBEE012B74A; Wed, 13 Apr 2011 22:19:06 -0700 (PDT) Message-ID: <4DA67BBE.9050606@taht.net> Date: Wed, 13 Apr 2011 22:44:46 -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: bloat@lists.bufferbloat.net, Brian Clapper Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Bloat] ECN blocking router found 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: Fri, 15 Apr 2011 00:09:48 -0000 In my travels this month I have been testing ECN enablement at homes and hotels everywhere I go. Until today, I was able to have the following settings for ECN on my laptop everywhere I've been. net.ipv4.tcp_ecn=1 #net.ipv6.tcp_ecn=0 net.ipv4.tcp_sack=1 net.ipv4.tcp_dsack=1 However, I got to visit Brian Clapper [1] (friend/co-author of gnugol) tonight, and discovered that his fairly recently purchased router, a: Etherfast Cable/DSL router Model BEFSR41 Firmware version 2.0.0.4 flat out refused to pass ECN enabled connection attempts (returning an ICMP unreachable message) He'd not noticed the problem because ubuntu 10.4 (at least, he also runs bsd) has tcp_ecn=2, which so far as I know "tries" a ECN enabled connect then falls back to not using it. I'm bummed that such a recent router doesn't pass ECN, and will look into the problem further in the morning. So I think we must use tcp_ecn = 1 to TEST to make sure ECN is being passed, and tcp_ecn=2 as the default recommendation. Perhaps we can synthesize TCP streams to more directly test ECN capability in the future somehow as part of our testing tools. Are there any tools that synthesize TCP/ip we could use as a starting point? [1] http://brizzled.clapper.org/