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Re: [lwip-users] TCP [TCP Window Update]

From: Kieran Mansley
Subject: Re: [lwip-users] TCP [TCP Window Update]
Date: Tue, 11 Aug 2009 09:01:39 +0100

On Mon, 2009-08-10 at 20:49 -0300, Alain Mouette wrote

> I am using lwip 1.3.0.

The window update code changed significantly between 1.3.0 and 1.3.1, so
it might be worth upgrading to see if this has already been solved for
you.  There were some problems with the old code, so it was completely

> the (ii) option seems to fullfill my needs :) can you give me a hint on 
> where to look for that? Bigger packet sizes are not important because 
> they don't happen very often and thus wil cause no traffic cost problem.

In tcp_recved() (src/core/tcp.c) there is now some code that looks like

  /* If the change in the right edge of window is significant (default
   * watermark is TCP_WND/2), then send an explicit update now.
   * Otherwise wait for a packet to be sent in the normal course of
   * events (or more window to be available later) */
  if (wnd_inflation >= TCP_WND_UPDATE_THRESHOLD) 

You should be able to configure TCP_WND_UPDATE_THRESHOLD and see the
change that you require, but with the current code it will only send an
explicit window update if there is a change greater than half the window
(so a lot more than 11 bytes!) 


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