From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-la0-x233.google.com (mail-la0-x233.google.com [IPv6:2a00:1450:4010:c03::233]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 111B821F306 for ; Sun, 12 Apr 2015 17:45:49 -0700 (PDT) Received: by layy10 with SMTP id y10so46269183lay.0 for ; Sun, 12 Apr 2015 17:45:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=y++9drgG8lWwRds6a4XvcKT5p3px15DwL8rx23vkZTc=; b=OZ7uFo4DK1uOv3eseJ3Mpz6RY32NGY1+y2pU0NWp6CKuw0AvTigynCRDRop8kVzVMG C0DtuMbA+6JQXYRpxIEL22dHvno5Y21ZCiFSNjTe+9wt+PuYRpO9hY4KKKxJ/STe1ulu wmYcan4BCcktWWNw5TReA9NVegGrHxTnQtUzrbSddrIMmsDMDujwGAplq/C7KmfIn1nW fJ12ZnRxI1vY+V+HRxsCOxKNwgF+ic9GypV+6G1YlnaZl7HjGXjVhQgarAVEV92q5Skt SwUrt4g35L1SdVHxENzqxrrDwHs5WVFX3Vf7V758Ad/6DSmPuVIQLXkSczkeAvICDNZZ ASaQ== X-Received: by 10.112.170.100 with SMTP id al4mr11043465lbc.42.1428885947756; Sun, 12 Apr 2015 17:45:47 -0700 (PDT) Received: from bass.home.chromatix.fi (87-93-27-145.bb.dnainternet.fi. [87.93.27.145]) by mx.google.com with ESMTPSA id f7sm1303363lam.17.2015.04.12.17.45.40 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 12 Apr 2015 17:45:46 -0700 (PDT) Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) From: Jonathan Morton In-Reply-To: Date: Mon, 13 Apr 2015 03:45:35 +0300 Content-Transfer-Encoding: quoted-printable Message-Id: <1D75F7D7-4EA1-47CB-8CA0-51144C58857E@gmail.com> References: <68E872EE-C0D3-4091-97C9-19596BF98AEB@gmail.com> To: Sebastian Moeller X-Mailer: Apple Mail (2.2098) Cc: cake@lists.bufferbloat.net Subject: Re: [Cake] #17 X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Apr 2015 00:46:18 -0000 > On 13 Apr, 2015, at 03:23, Sebastian Moeller wrote: >=20 > Ignore my gibberish below, that is almost all required: = ceil(len+additional_per_packet_overhead/48)*53 seems the winner ;) = Effectively this is what stab should offer, but its implementation with = a table has issues if packets are larger than the table estimated=85 The other problem with stab is that the configuration is awfully verbose = - pretty much what I was trying to avoid with cake. I=92ll admit that a = table lookup can be faster than a calculation (under favourable = circumstances), but exposing those sorts of implementation details to = userspace is just going to give people headaches while they try to = figure out what to put and why. That=92s a recipe for people (and, more seriously, CPE vendors) getting = it wrong. So cake just has that simple =93atm=94 flag, which adds roughly the = right amount of overhead for cell-framing already. Any optimisations to = that calculation (which are certainly possible) are an internal matter = and not for public consumption. It could be refined by adding an additional, orthogonal setting for = non-cell framing overhead, which would be added before the cell-framing = calculation; this would allow adding the 8 bytes of PPPoE framing and/or = the 2 bytes of Ethernet VLAN tag, for people who want to get it exactly = right. Whether these are simple, self-descriptive flags which can be = combined for the desired effect, or a numeric parameter which must be = set up, is open for discussion. All of this will help with setting cake=92s shaper closer to, and = eventually perhaps *at* the physical link rate. The relative lack of = bursting from cake=92s shaper already allows some of that, since it=92s = no longer necessary to allow the initial burst from the token bucket to = drain from the dumb FIFO downstream. - Jonathan Morton