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 From:  "Chad R. Larson" <clarson at eldocomp dot com>
 To:  Adam Nellemann <adam at nellemann dot nu>
 Cc:  Jose Iadicicco <joseiadicicco at yahoo dot com>, "m0n0wall at lists dot m0n0 dot ch" <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] Re: m0n0 - traffic_shaper
 Date:  Wed, 2 Jun 2004 17:22:57 -0700
Adam Nellemann wrote:

> Hi Jose,
> 
> Here's the theory behind why inbound shaping doesn't work (or at least
> doesn't work well) If anyone has knowledge to the contrary, please post:
> 
> = = =
> 
> Since there is no built-in "traffic control messages" (or similar) in
> TCP/IP, there is no way for m0n0wall to "tell" the device(s) on the
> "other side" of your WAN link (such as the router at your ISP's end of
> your ADSL line) to stop sending packets (or do so at a slower rate).
>

To the contrary.  The TCP "advertised window" is exactly that control.

When a TCP packet is sent, one of the values in the header is the 
number of bytes the sender is willing to receive in return.  An ACK 
for all bytes and a window of 0 would be very similar to a CTL-S on a 
serial link, but varying the size of the window allows a smoother 
control of the flow than a simple start/stop.

          -crl
--
Chad R. Larson (CRL22)    chad at eldocomp dot com
   Eldorado Computing, Inc.   602-604-3100
      5353 North 16th Street, Suite 400
        Phoenix, Arizona   85016-3228

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