From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from shiva.jussieu.fr (shiva.jussieu.fr [134.157.0.129]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by huchra.bufferbloat.net (Postfix) with ESMTPS id 1FC8E21F0E2; Mon, 14 May 2012 11:31:22 -0700 (PDT) Received: from hydrogene.pps.jussieu.fr (hydrogene.pps.jussieu.fr [134.157.168.1]) by shiva.jussieu.fr (8.14.4/jtpda-5.4) with ESMTP id q4EIUs8d035189 ; Mon, 14 May 2012 20:31:07 +0200 (CEST) X-Ids: 168 Received: from lanthane.pps.jussieu.fr (lanthane.pps.jussieu.fr [134.157.168.57]) by hydrogene.pps.jussieu.fr (Postfix) with ESMTPS id C6333C0F62; Mon, 14 May 2012 20:30:53 +0200 (CEST) Received: from jch by lanthane.pps.jussieu.fr with local (Exim 4.77) (envelope-from ) id 1SU02n-00082g-Kr; Mon, 14 May 2012 20:30:53 +0200 From: Juliusz Chroboczek To: dave taht References: <4FB129EC.90200@gmail.com> <7imx5a3b4t.fsf@lanthane.pps.jussieu.fr> <1337018621.8512.592.camel@edumazet-glaptop> <4FB14C6E.7030604@gmail.com> Date: Mon, 14 May 2012 20:30:53 +0200 In-Reply-To: <4FB14C6E.7030604@gmail.com> (dave taht's message of "Mon, 14 May 2012 11:18:22 -0700") Message-ID: <7i8vguvcma.fsf@lanthane.pps.jussieu.fr> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit X-Miltered: at jchkmail.jussieu.fr with ID 4FB14F5E.001 by Joe's j-chkmail (http : // j-chkmail dot ensmp dot fr)! X-j-chkmail-Enveloppe: 4FB14F5E.001/134.157.168.1/hydrogene.pps.jussieu.fr/hydrogene.pps.jussieu.fr/ Cc: codel@lists.bufferbloat.net, bloat@lists.bufferbloat.net Subject: Re: [Codel] [Bloat] better tc support for bittorrent/diffserv X-BeenThere: codel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: CoDel AQM discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 14 May 2012 18:31:23 -0000 > I think, but am not certain, jch is referring to the problem of > negotiating ecn over uTP. No, I was actually unaware that Linux allows one to set the ECN bits from userspace. OTOH, you're right that µTP doesn't currently support ECN. Not that it matters much, ECN is useful for interactive connections (where it can avoid a one-RTT delay due to a packet loss) but pretty useless for bulk transfers[1]. On a related note, the µTP framing is pretty horrible IMHO, and LEDBAT is better implemented within TCP. Unfortunately, this is not possible under Windows (yeah, I got one of the µTorrent guys to contact Microsoft on this subject). On a note related to the related note, Transmission already has the ability to make use of a non-default congestion controller for TCP: http://www.pps.jussieu.fr/~jch/software/bittorrent/tcp-congestion-control.html -- Juliusz [1] Marek Malowidzki, Simulation-based Study of ECN Performance in RED Networks, In Proc. SPECTS'03. 2003.