From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-14-ewr.dyndns.com (mxout-048-ewr.mailhop.org [216.146.33.48]) by lists.bufferbloat.net (Postfix) with ESMTP id DA27C2E07AF for ; Fri, 15 Apr 2011 10:40:21 -0700 (PDT) Received: from scan-12-ewr.mailhop.org (scan-12-ewr.local [10.0.141.230]) by mail-14-ewr.dyndns.com (Postfix) with ESMTP id D0EE19CFEDA for ; Fri, 15 Apr 2011 17:40:20 +0000 (UTC) X-Spam-Score: -4.0 (----) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 17.151.62.49 Received: from mail-out.apple.com (bramley.apple.com [17.151.62.49]) by mail-14-ewr.dyndns.com (Postfix) with ESMTP id E881B9CD82E for ; Fri, 15 Apr 2011 17:40:13 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; CHARSET=US-ASCII Received: from relay15.apple.com ([17.128.113.54]) by mail-out.apple.com (Oracle Communications Messaging Exchange Server 7u4-20.01 64bit (built Nov 21 2010)) with ESMTP id <0LJP00IW8FOXWK20@mail-out.apple.com> for bloat@lists.bufferbloat.net; Fri, 15 Apr 2011 10:40:13 -0700 (PDT) X-AuditID: 11807136-b7c6bae000004a34-e7-4da882fdc3ea Received: from rui-mac-pro.apple.com (rui-mac-pro.apple.com [17.193.13.194]) (using TLS with cipher AES128-SHA (AES128-SHA/128 bits)) (Client did not present a certificate) by relay15.apple.com (Apple SCV relay) with SMTP id 5A.60.18996.DF288AD4; Fri, 15 Apr 2011 10:40:13 -0700 (PDT) From: Rui Paulo In-reply-to: <4DA67BBE.9050606@taht.net> Date: Fri, 15 Apr 2011 10:40:13 -0700 Message-id: <7DD875AA-B91E-4F7A-85F4-61A6BA40567A@apple.com> References: <4DA67BBE.9050606@taht.net> To: Dave Taht X-Mailer: Apple Mail (2.1084) X-Brightmail-Tracker: AAAAAA== Cc: Brian Clapper , 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 17:40:22 -0000 On Apr 13, 2011, at 9:44 PM, 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 > > 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? Are you looking for something like this? http://www.icir.org/tbit/index.html#ECN Regards, -- Rui Paulo