From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael Chan" Subject: Re: time for TCP ECN defaulting to on? Date: Tue, 04 Nov 2008 17:16:03 -0800 Message-ID: <1225847763.11369.43.camel@HP1> References: <6278d2220811040632u7a36d68ekad5de517fd0671bb@mail.gmail.com> <49107543.5080207@blueteddy.net> <20081104.145242.112948002.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: "linux-kernel@blueteddy.net" , "daniel.blueman@gmail.com" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "linux-net@vger.kernel.org" To: "David Miller" Return-path: In-Reply-To: <20081104.145242.112948002.davem@davemloft.net> Sender: linux-net-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 2008-11-04 at 14:52 -0800, David Miller wrote: > From: Dave Hudson > Date: Tue, 04 Nov 2008 16:16:03 +0000 > > > Daniel J Blueman wrote: > > > Is it time to enable TCP ECN per default and get the benefits, since > > > router support has been around and known-about for really considerable > > > time? > > > Perhaps it should be a question of enabling it, and educating people > > > to disable it if they run into issues, since we'll probably be in the > > > same situation in 5 years...and it'll be some time before these > > > kernels hit devices/servers anyway. > > > Daniel > > > > Unfortunately I think you'll find there are sufficiently large > > numbers of broken SOHO routers out there that if you try this you'll > > cause a lot of problems. The problems range from no connectivity to > > in a few extreme cases routers actually crashing or behaving in very > > unpredictable ways. Here's one summary that got presented to the > > IETF about 18 months ago: > > > > http://www.ietf.org/proceedings/07mar/slides/tsvarea-3/sld6.htm > > Another issue is that, even if we turn it on by default, it won't > be on for a significant number of network cards out there. > > This is because TSO, which is on by default, doesn't support ECN > in many implementations. I think this is no longer a limitation. The GSO code will take care of ECN properly if the hardware does not support it when doing TSO.