From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-32-ewr.dyndns.com (mxout-122-ewr.mailhop.org [216.146.33.122]) by lists.bufferbloat.net (Postfix) with ESMTP id B517B2E001D for ; Sun, 3 Apr 2011 09:36:24 -0700 (PDT) Received: from scan-31-ewr.mailhop.org (scan-31-ewr.local [10.0.141.237]) by mail-32-ewr.dyndns.com (Postfix) with ESMTP id B60526FA3B8 for ; Sun, 3 Apr 2011 16:36:23 +0000 (UTC) X-Spam-Score: 0.0 () X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 134.157.0.129 Received: from shiva.jussieu.fr (shiva.jussieu.fr [134.157.0.129]) by mail-32-ewr.dyndns.com (Postfix) with ESMTP id 29DA06F8D52 for ; Sun, 3 Apr 2011 16:36:16 +0000 (UTC) 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 p33GZlqX009668 ; Sun, 3 Apr 2011 18:36:00 +0200 (CEST) X-Ids: 165 Received: from lanthane.pps.jussieu.fr (lanthane.pps.jussieu.fr [134.157.168.57]) by hydrogene.pps.jussieu.fr (Postfix) with ESMTPS id 61F3AC005F; Sun, 3 Apr 2011 18:35:46 +0200 (CEST) Received: from jch by lanthane.pps.jussieu.fr with local (Exim 4.72) (envelope-from ) id 1Q6QHC-0007f1-7G; Sun, 03 Apr 2011 18:35:46 +0200 From: Juliusz Chroboczek To: Jonathan Morton References: <7imxklz5vu.fsf@lanthane.pps.jussieu.fr> <1300999472.12456.22.camel@amd.pacdat.net> Date: Sun, 03 Apr 2011 18:35:46 +0200 In-Reply-To: <1300999472.12456.22.camel@amd.pacdat.net> (richard@pacdat.net's message of "Thu, 24 Mar 2011 13:44:32 -0700") Message-ID: <7ik4fbz40t.fsf@lanthane.pps.jussieu.fr> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Miltered: at jchkmail.jussieu.fr with ID 4D98A1E3.002 by Joe's j-chkmail (http : // j-chkmail dot ensmp dot fr)! X-j-chkmail-Enveloppe: 4D98A1E3.002/134.157.168.1/hydrogene.pps.jussieu.fr/hydrogene.pps.jussieu.fr/ Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] Thoughts on Stochastic Fair Blue 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: Sun, 03 Apr 2011 16:36:25 -0000 Sorry for the delay, but I wanted to think this over. > My second observation is that marking and dropping both happen at the > tail of the queue, not the head. This delays the congestion information > reaching the receiver, and from there to the sender, by the length of > the queue It's very difficult to drop at the head of the queue in SFB, since we'd need to find a suitable packet that's in the same flow. Since SFB makes heroic efforts to keep the queue size small, this shouldn't make much of the difference. Your suggestion is most certainly valid for plain BLUE. > Another observation is that packets are not re-ordered by SFB, which > (given the Bloom filter) is potentially a missed opportunity. What's your suggestion? > However, they can be re-ordered in the current implementation by > using child qdiscs such as SFQ I don't see how that buys you anything. SFB is very aggressive with dropping packets when under congestion, and the packet drop happens *before* the child qdisc gets a chance to see the packet; hance, putting SFQ below SFB won't buy you much, it'll just reorder packets in the small queue that SFB allows. Or am I missing something? -- Juliusz