From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-21-ewr.dyndns.com (mxout-095-ewr.mailhop.org [216.146.33.95]) by lists.bufferbloat.net (Postfix) with ESMTP id 5519C2E03C0 for ; Thu, 14 Apr 2011 17:09:08 -0700 (PDT) Received: from scan-21-ewr.mailhop.org (scan-21-ewr.local [10.0.141.243]) by mail-21-ewr.dyndns.com (Postfix) with ESMTP id 43FE54F4A for ; Thu, 14 Apr 2011 14:43:37 +0000 (UTC) X-Spam-Score: 0.0 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 69.164.215.38 Received: from mail.ardentex.com (yore.ardentex.com [69.164.215.38]) by mail-21-ewr.dyndns.com (Postfix) with ESMTP id 12C3679F for ; Thu, 14 Apr 2011 14:43:20 +0000 (UTC) Received: from atlas.inside.ardentex.com (c-68-81-97-191.hsd1.pa.comcast.net [68.81.97.191]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.ardentex.com (Postfix) with ESMTPSA id EFF526264; Thu, 14 Apr 2011 14:43:18 +0000 (UTC) X-DKIM: Sendmail DKIM Filter v2.8.3 mail.ardentex.com EFF526264 Message-ID: <4DA70806.9020002@ardentex.com> Date: Thu, 14 Apr 2011 10:43:18 -0400 From: Brian Clapper 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: Dave Taht References: <4DA67BBE.9050606@taht.net> In-Reply-To: <4DA67BBE.9050606@taht.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Thu, 14 Apr 2011 17:12:32 -0700 Cc: bloat@lists.bufferbloat.net Subject: Re: [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 00:09:08 -0000 On 04/14/2011 12:44 AM, Dave Taht wrote: > 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 NOTE: Per the support web site for this device, firmware revision 2.00.4 is the latest. > 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/ > -- Brian Clapper, bmc@ardentex.com President & Principal Consultant: ArdenTex, Inc. 610.247.4395 (phone) 484.932.1270 (fax) www.ardentex.com