[ previous ] [ next ] [ threads ]
 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.

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


This message is intended for the sole use of the individual and entity to whom it is addressed, and
may contain information that is privileged, confidential and exempt from disclosure under applicable
law. If you are not the intended addressee, nor authorized to receive for the intended addressee,
you are hereby notified that you may not use, copy, disclose or distribute to anyone the message or
any information contained in the message. If you have received this message in error, please
immediately advise the sender by reply email, and delete the message. Thank you.