From owner-freebsd-isp Sun Mar 11 18:18:34 2001 Delivered-To: freebsd-isp@freebsd.org Received: from misery.sdf.com (misery.sdf.com [204.244.213.49]) by hub.freebsd.org (Postfix) with ESMTP id 2FB9637B71A for ; Sun, 11 Mar 2001 18:18:24 -0800 (PST) (envelope-from tom@sdf.com) Received: from tom (helo=localhost) by misery.sdf.com with local-esmtp (Exim 2.12 #1) id 14cHu2-0006ZY-00; Sun, 11 Mar 2001 18:17:42 -0800 Date: Sun, 11 Mar 2001 18:17:20 -0800 (PST) From: Tom Samplonius To: Alex Huppenthal Cc: freebsd-isp@FreeBSD.ORG Subject: Re: ATM and traffic shaping In-Reply-To: <004101c0aa73$4bdefdc0$1800a8c0@d7k> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-isp@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Sun, 11 Mar 2001, Alex Huppenthal wrote: > It turns out that traffic shaping for ATM means being able to delay each > cell to a specific egress ('transmit' in english) rate. Yes, exactly. And many switches are configured to drop non-conforming cells (cells that exceed the allowable cell-per-second rate). I wouldn't recommend that anyone attempt ATM without understanding all the service categories and parameters. However, it somewhat depends on the category of service that you receive. There are lots of possibilities: ubr, cbr, rt-vbr, nrt-vbr, and vbr. The maximum cell rate isn't always a simple thing, as they interact with the mcr, pcr, mbs, and scr parameters. Since you are using your own ATM switch, I'm surprised that you can't let your switch buffer cells for you, rather than discard them. For instance, if your ATM provider has given you a cbr service with 10K cells/second rate, just let FreeBSD run ubr into the switch. But it really depends on your ATM service provider. I have a very expensive switch with an ATM card and multiple ethernet ports. My ATM service provider is providing an abr with a pcr of 10Mbps service. Their switch will buffer and pace out traffic for me, so I have the link setup as ubr on my end. In fact, it was the configuration they recommended. Tom To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message