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Date:      Wed, 11 Sep 1996 23:17:07 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        hackers@freebsd.org
Cc:        wollman@lcs.mit.edu, phk@freebsd.org
Subject:   Changing default TCP window size ?
Message-ID:  <199609112117.XAA08985@labinfo.iet.unipi.it>

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How do I force TCP (or the OS) to use a window size different from the
default 16K ?

The following code
    
    mywin=DESIRED_WINDOW_SIZE;
    setsockopt(f, SOL_SOCKET, SO_SNDBUF, (char *)&mywin, sizeof mywin)
    
appears to set the value correctly (it can be read back with 
getsockopt) but then it appears not to have any effect on TCP
(monitoring the connection with netstat -na always shows a Send-Q 
around 16KB, and the throughput in window-limited configurations 
remains unchanged).
 
I have also tried to alter net.inet.tcp.sendspace but with no
effect.
 
I am asking because I would really like to try out large windows
and check if RFC1323 extensions really work (I have been told there
are some unspecified problems).

        Thanks
        Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================



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