From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-gg0-f171.google.com (mail-gg0-f171.google.com [209.85.161.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id AC38A201A91 for ; Mon, 7 May 2012 12:36:05 -0700 (PDT) Received: by ggki1 with SMTP id i1so1481953ggk.16 for ; Mon, 07 May 2012 12:36:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:message-id:date:from:organization:user-agent:mime-version:to :cc:subject:references:in-reply-to:content-type :content-transfer-encoding; bh=yjrcl+kdg1tjZwAF0T/daWerE6U9GvlaKzI5hTnj0Nk=; b=KdSIHLI5hHHtGBpmKMtLnv9YE+Fhvv2JaXuhAKvVmUwvtNdnpQ+9nZVDcn9Rzsi2vQ LZ6v2JIcq1xn9z8DCfQxcqvM8fGAI7Zh4JpYNGiFpWB0y848rYNeSOmWqSWPuWBx4bZ3 uFIS2lR5JDyDAZsOu0FSMgg26wk/lhOxmArmE9/yvbrxZuBsyBDemn/9kFlahw4H4GrO KgktoNOr7Q1w1g2iTbK80Ho+8O2u+t+d5IbAVv6ktqR8eJJM9lCPKoBmsGpndqmn5Ucx HjRNFZaF44yD/FSFNleSufGOAYSF7d9Mlh5Rzp/PE89nIYiRZ8E4/a0vojXb/+aNeROW 4FJw== Received: by 10.236.116.169 with SMTP id g29mr20391840yhh.54.1336419364543; Mon, 07 May 2012 12:36:04 -0700 (PDT) Received: from [192.168.1.81] (c-50-138-162-108.hsd1.ma.comcast.net. [50.138.162.108]) by mx.google.com with ESMTPS id n14sm29028856anl.11.2012.05.07.12.36.03 (version=SSLv3 cipher=OTHER); Mon, 07 May 2012 12:36:03 -0700 (PDT) Sender: Jim Gettys Message-ID: <4FA82422.9040500@freedesktop.org> Date: Mon, 07 May 2012 15:36:02 -0400 From: Jim Gettys Organization: Bell Labs User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Eric Dumazet References: <1336246349-20228-1-git-send-email-dave.taht@bufferbloat.net> <4FA7FBC7.2040501@hp.com> <1336410626.3752.2329.camel@edumazet-glaptop> <4FA805F9.20004@hp.com> <1336412079.3752.2333.camel@edumazet-glaptop> <4FA81549.5060609@freedesktop.org> <4FA8197C.4090909@freedesktop.org> <1336418211.3752.2353.camel@edumazet-glaptop> In-Reply-To: <1336418211.3752.2353.camel@edumazet-glaptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , codel@lists.bufferbloat.net, Dave Taht Subject: Re: [Codel] [PATCH 1/2] codel: Controlled Delay AQM 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, 07 May 2012 19:36:06 -0000 On 05/07/2012 03:16 PM, Eric Dumazet wrote: > On Mon, 2012-05-07 at 14:50 -0400, Jim Gettys wrote: > >> You want to turn it on in CeroWrt: sure. Expert audience, who may be >> able to notice when things go sour, fine.... >> >> Neither you, nor I are expert at the current state of ECN in the global >> Internet: but Steve Bauer is. We can have that conversation with him >> shortly. >> >> So for now "First, do no harm" should be our mantra.... >> >> So the upstream patch default state should be off. We don't want to mix >> "codel doesn't work" with "ecn is busted someplace", as it gets its trials. >> > ecn is negociated by peers, not a qdisc. > > ecn at qdisc level is only marking an already enabled ECN packet. > > Since most packets are not ECN enabled, they are dropped instead. That's certainly the way ECN is supposed to work right now. > > If you read my ECN addition to Codel, you can see its disabled by > default already. Its a toy for early adopters. I think it is safe for it to behave the rest of the way Linux ECN support does right now: it only gets used if the peer requests it. Not clear to me there needs to be/should be any option at all: the last conversation I had with Steve Bauer was that something north of 20% of conversations were ECN capable. Is there one for the other instances of ECN support in Linux? If so, it should be keyed by the same variable, and not be a one-off for codel. If you wanted to test ECN separately from drop with codel, then you'd just request ECN in the conversation (by default, OS's don't normally request ECN today, as the remaining brokenness gets sorted out). - Jim