From owner-freebsd-net@FreeBSD.ORG  Mon Dec 10 20:20:14 2007
Return-Path: <owner-freebsd-net@FreeBSD.ORG>
Delivered-To: freebsd-net@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 7F69016A417
	for <freebsd-net@freebsd.org>; Mon, 10 Dec 2007 20:20:14 +0000 (UTC)
	(envelope-from rizzo@icir.org)
Received: from xorpc.icir.org (xorpc.icir.org [192.150.187.68])
	by mx1.freebsd.org (Postfix) with ESMTP id 67C4613C469
	for <freebsd-net@freebsd.org>; Mon, 10 Dec 2007 20:20:14 +0000 (UTC)
	(envelope-from rizzo@icir.org)
Received: from xorpc.icir.org (localhost [127.0.0.1])
	by xorpc.icir.org (8.12.11/8.13.6) with ESMTP id lBAK3raM040753;
	Mon, 10 Dec 2007 12:03:53 -0800 (PST)
	(envelope-from rizzo@xorpc.icir.org)
Received: (from rizzo@localhost)
	by xorpc.icir.org (8.12.11/8.12.3/Submit) id lBAK3rHw040752;
	Mon, 10 Dec 2007 12:03:53 -0800 (PST) (envelope-from rizzo)
Date: Mon, 10 Dec 2007 12:03:53 -0800
From: Luigi Rizzo <rizzo@icir.org>
To: Chuck Swiger <cswiger@mac.com>
Message-ID: <20071210120353.B40679@xorpc.icir.org>
References: <475D6FD7.2000500@mail.ru>
	<DCFF3417-FC01-4F2C-ACA5-03CC0881DE59@mac.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5.1i
In-Reply-To: <DCFF3417-FC01-4F2C-ACA5-03CC0881DE59@mac.com>;
	from cswiger@mac.com on Mon, Dec 10, 2007 at 11:22:33AM -0800
Cc: rihad <rihad@mail.ru>, freebsd-net@freebsd.org
Subject: Re: Pipe queues
X-BeenThere: freebsd-net@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Networking and TCP/IP with FreeBSD <freebsd-net.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-net>
List-Post: <mailto:freebsd-net@freebsd.org>
List-Help: <mailto:freebsd-net-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-net>,
	<mailto:freebsd-net-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 10 Dec 2007 20:20:14 -0000

On Mon, Dec 10, 2007 at 11:22:33AM -0800, Chuck Swiger wrote:
> On Dec 10, 2007, at 8:56 AM, rihad wrote:
> > Hi,
> >
> > I'm having a hard time to understand what pipe queues are with  
> > respect to bandwidth limitation. ipfw(8) and dummynet(4) manuals  
> > didn't help me much.
> 
> Pipes and queues are two different things; a pipe simulates a network  
> link, and a queue is used to hold packets which are backlogged because  
> they are arriving faster than the outbound link (ie, a pipe) can  
> transmit them.
> 
> > How does dummynet's traffic shaping function?
> 
> It uses a variant of weighted fair queuing.

actually the shaping uses a leaky bucket algorithm.
The weighted fair queuing is the queue management scheme used
when you have multiple queues attached to the same pipe

cheers
luigi