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From Mark Montague <>
Subject Re: [users@httpd] Version of TCP
Date Mon, 26 Sep 2011 10:54:00 GMT
On September 26, 2011 4:25 , Dusan Geratovic <> 
> Which version of TCP protocol does the Apache Server 2.2 use? I have 
> noticed that in case of packet loss TCP window does not shrink to the 
> half size (like standard version does), but to the 20, 30% of its 
> original size. I suppose that the some modified version is used (High 
> Speed TCP or something like that).

Apache HTTP Server uses the version of TCP provided by the operating 
system it is running on.   The Apache Portable Runtime (APR) library is 
used to provide a consistent interface to Apache HTTP Server regardless 
of operating-system-specific variations.  See and

I'm not aware of anything in Apache HTTP Server or APR that controls TCP 
windowing, although they do use the TCP_NODELAY, TCP_CORK, and 
TCP_NOPUSH socket options: see

 From my limited knowledge, I suspect the windowing behavior you are 
seeing is due to behavior of your operating system kernel.

   Mark Montague

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