Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753663AbYKGSoB (ORCPT ); Fri, 7 Nov 2008 13:44:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751475AbYKGSnr (ORCPT ); Fri, 7 Nov 2008 13:43:47 -0500 Received: from yx-out-2324.google.com ([74.125.44.28]:55301 "EHLO yx-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751474AbYKGSnq (ORCPT ); Fri, 7 Nov 2008 13:43:46 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=gc6gka0YheemZ8sn8d9qVfpxkI+OVC0vcoOEXEB7iZAuPkK0c4pFqmgtALa5OB+z3h p20tJ+ivqE2/AWVuWIr6t9G1HFKvbgwlmb4hGN4wzLKZpgWA0qAMaaBJJds3uT7smUWS LaRT/zk8y0+VS8HvQVC0b/B8iwySuJUxZNx64= Message-ID: <1e41a3230811071038p58a55cc6g9103b891ca15a1df@mail.gmail.com> Date: Fri, 7 Nov 2008 10:38:26 -0800 From: "John Heffner" To: "David Newall" Subject: Re: time for TCP ECN defaulting to on? Cc: "Alan Cox" , "Dave Hudson" , "=?ISO-8859-1?Q?Ilpo_J=E4rvinen?=" , "Mikael Abrahamsson" , "David Miller" , daniel.blueman@gmail.com, LKML , Netdev , linux-net@vger.kernel.org In-Reply-To: <491454A3.1040802@davidnewall.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <6278d2220811040632u7a36d68ekad5de517fd0671bb@mail.gmail.com> <20081105.151015.206163697.davem@davemloft.net> <4914240F.7050701@blueteddy.net> <20081107142950.13906925@lxorguk.ukuu.org.uk> <491454A3.1040802@davidnewall.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2042 Lines: 45 The IETF has provided a spec, and additional documents on deployment issues. They have provided all the guidance they are going to. It's now up to implementers to weigh the trade-offs. My own observations and opinions, for what they're worth: Turning on ECN doesn't hurt as much as it used to. Back in the early '00s, there were a lot of devices sold especially to financial institutions to "protect" their web sites. These devices dropped any packets with (previously) reserved header bits set, because some people used these as a covert information channel. I believe these devices are not as common as they once were, but there are still a few big sites that black hole these packets. (I know that southwest.com is still an offender.) I have not actually heard of any issues with consumer-grade stuff, but that may be because ECN has been disabled by default for so long. Almost no network operators turn on ECN marking in their routers. In fact, almost none care to do any sort of AQM. The practical benefits of ECN are still somewhat unclear for most people. For example, it can help with latency-sensitive applications, but mostly requires a big queue to work well, so doesn't help as much as you would hope. There are some interesting ideas on how to better use ECN information, but these are mostly still research. ECN black hole detection is pretty simple, and I don't see much reason not to do it. -John On Fri, Nov 7, 2008 at 6:45 AM, David Newall wrote: > Isn't this a question for the IETF to answer? Are they saying turn on > ECN now? > -- > To unsubscribe from this list: send the line "unsubscribe linux-net" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/