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Date: Wed, 11 Mar 2009 12:42:23 +0000
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Subject: Re: torrent client traffic shaping question
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On Wed, 11 Mar 2009 11:13:16 +0200
Brent Clark <brentgclarklist@gmail.com> wrote:

> Hiya
> 
> I got this question to ask, and I was hoping the TCP/IP gurus would be
> able to help me understand this.
> 
> K you know how with traffic shapping you can control only the traffic
> leaving you, how it is that torrent clients say they can control the
> download as well as the upload. I would think the client can only
> control the upload.

If the client reads from a TCP socket slower than the data is coming-in,
the buffers fill-up and the sliding-window algorithm in TCP causes the
sending side to slow down.

A traffic shaper could efficiently regulate downloads by proxying TCP.
And even though PF does some limited TCP proxying, unfortunately
dummynet and altq  work at the IP level.