From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (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 8277E21F2DC for ; Thu, 11 Jun 2015 04:16:26 -0700 (PDT) Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 94ECE36506A; Thu, 11 Jun 2015 11:16:24 +0000 (UTC) Received: from localhost (ovpn-116-130.ams2.redhat.com [10.36.116.130]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t5BBGKYt025560; Thu, 11 Jun 2015 07:16:22 -0400 Date: Thu, 11 Jun 2015 13:16:15 +0200 From: Jesper Dangaard Brouer To: Sebastian Moeller Message-ID: <20150611131615.20b1648f@redhat.com> In-Reply-To: <0A0D06AB-CC83-4D99-80C6-8E7822C8707C@gmx.de> References: <5572F7E0.3060602@darbyshire-bryant.me.uk> <0A0D06AB-CC83-4D99-80C6-8E7822C8707C@gmx.de> Organization: Red Hat Inc. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 Cc: bloat@lists.bufferbloat.net Subject: Re: [Bloat] ADSL, ATM drivers, bloat, education & confusion 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: Thu, 11 Jun 2015 11:16:54 -0000 On Sat, 6 Jun 2015 16:29:15 +0200 Sebastian Moeller wrote: > On Jun 6, 2015, at 15:38 , Kevin Darbyshire-Bryant wrote: >=20 [...] > > The problem I have is setting outbound rate limiting. I was hoping > > that 'cake' without the 'bandwidth' parameter would work on the > > 'backpressure' from the ATM(?) driver, sadly this wasn't the case > > and so setting a bandwidth limit (I'm not in a position to test the > > new keywords for ATM encapsulation etc yet) was the only way > > forward. =20 >=20 > This is rather important to get right, ATM=E2=80=99s arcane 48/53 > encapsulation only leaves 100*48/53 =3D 90.5% of the sync rate for > useable bits, and even those need to contain all the headers specific > to your line (plus AAL5=E2=80=99s unfortunate choice of fitting each pack= et > into an integer number of ATM cells), mean that without AQM taking > the link layer encapsulation into account you need to aim for roughly > 80-85% of the sync rates on and ATM link. With a link that disappears > often I currently would recommend sqm-scripts as weapon of choice > (you should be able to get cake into sqm-scripts) as the IFB needs to > be set up again after the =E2=80=9Cconnected=E2=80=9D interface reappears= , which > current sqm-scripts should do for you... That is true, the ATM overhead on ADSL is very important to get right for your ratelimiting work as intended (that is you gain control over the queue). The iproute2 "tc" have supported option "linklayer atm" and "overhead" for quite some time now (since 2008). All the rate_tables based schedulers (e.g. HTB, TBF) have these options. There is also the more generic "stab" that allow linklayer adaptation to work for any qdisc. See man tc-stab [1] --=20 Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer [1] http://manpages.ubuntu.com/manpages/precise/man8/tc-stab.8.html