From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from vps.slashdirt.org (vps.slashdirt.org [144.91.108.218]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 645883B29D for ; Thu, 17 Nov 2022 09:22:43 -0500 (EST) Received: from smtpclient.apple (tardis.herebedragons.eu [171.22.3.161]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by vps.slashdirt.org (Postfix) with ESMTPSA id 745AE60113; Thu, 17 Nov 2022 15:22:41 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 vps.slashdirt.org 745AE60113 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=slashdirt.org; s=mail; t=1668694962; bh=9yyczLWmA+wiMjPaoIX5NUz97YBR/K5Yjg3d7TH/X0k=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=EqEpoNMpA8t8iofW2AkaLTX0V4doZV0RAgXLimKTDZ+vnpATHR8hNORS5LwaRLULI 7HamCLgJt45ytEKgGFtJTuZbSslpHecVdT5oyeuJK7snHUFMpQg0Np+baMMoAN3BQv OHhz7Kaoa58qOsy21JwOedOEWb5P39a0dd+0F2NQ= Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3696.120.41.1.1\)) From: Thibaut In-Reply-To: Date: Thu, 17 Nov 2022 15:22:40 +0100 Cc: openwrt-devel , Cake List Content-Transfer-Encoding: quoted-printable Message-Id: <4D5AA477-1547-441F-900C-6DC70C824960@slashdirt.org> References: <386F2ED9-3D39-4A42-8982-742B5D4B417F@slashdirt.org> <4CF53FE3-D26A-4E32-8378-3B27BBB70AEF@slashdirt.org> To: Sebastian Moeller X-Mailer: Apple Mail (2.3696.120.41.1.1) Subject: Re: [Cake] Help untangling CAKE settings for FTTH X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 17 Nov 2022 14:22:43 -0000 Hi Sebastian, > Le 17 nov. 2022 =C3=A0 10:50, Sebastian Moeller a = =C3=A9crit : >=20 > Hi T. >=20 >=20 > so taking your proposa under consideration I canged the section that = threw you off course to read: >=20 >=20 > =E2=80=A2 Ethernet with Overhead: SQM can also account for the = overhead imposed by VDSL2 links - add 22 bytes of overhead (mpu 68). = Cable Modems (DOCSIS) set both up- and downstream overhead to 18 bytes = (6 bytes source MAC, 6 bytes destination MAC, 2 bytes ether-type, 4 = bytes FCS), to allow for a possible 4 byte VLAN tag it is recommended to = set the overhead to 18 + 4 =3D 22 (mpu 64). For FTTH the answer is less = clear cut, since different underlaying technologies have different = relevant per-packet-overheads; however underestimating the = per-packet-overhead is considerably worse for responsiveness than = (gently) overestimating it, so for FTTH set the overhead to 44 (mpu 84) = unless there is more detailed information about the true overhead on a = link available. > =E2=80=A2 None: All shaping below the physical gross-rate of a = link requires correct per-packet overhead accounting to be precise, so = None is only useful if approximate shaping is sufficient, say if you = want to clamp a guest network to at best ~50% of the available capacity = or similar tasks, but even then configuring an approximate correct = per-packet-overhead is recommended (overhead 44 (mpu 84) is a decent = default to pick). >=20 >=20 > I hope this is explicit enough. Yes this looks a lot better, thank you. Although I must confess that it certainly feels counter-intuitive that = for ethernet (and FTTH) we suggest a higher overhead than e.g. = VDSL2/cable (which themselves run off an ethernet interface). I would also like to see some info about ppp vs ethernet interface in = there (matching your previous email): unless you beat me to it I will = add it. I also think the =C2=AB details =C2=BB page needs to be reformatted a = bit, it=E2=80=99s very dense and relevant info is all over the place and = not very well organized. I=E2=80=99ll try to get around improving that. Thanks