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Date:      Mon, 10 Dec 2007 12:03:53 -0800
From:      Luigi Rizzo <rizzo@icir.org>
To:        Chuck Swiger <cswiger@mac.com>
Cc:        rihad <rihad@mail.ru>, freebsd-net@freebsd.org
Subject:   Re: Pipe queues
Message-ID:  <20071210120353.B40679@xorpc.icir.org>
In-Reply-To: <DCFF3417-FC01-4F2C-ACA5-03CC0881DE59@mac.com>; from cswiger@mac.com on Mon, Dec 10, 2007 at 11:22:33AM -0800
References:  <475D6FD7.2000500@mail.ru> <DCFF3417-FC01-4F2C-ACA5-03CC0881DE59@mac.com>

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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



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