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Date:      Thu, 19 Sep 1996 18:48:07 +1000 (EST)
From:      "Daniel O'Callaghan" <danny@panda.hilink.com.au>
To:        freebsd-hackers@freebsd.org
Subject:   TCP extensions breaking TCP.
Message-ID:  <Pine.BSF.3.91.960919183407.3641J-100000@panda.hilink.com.au>

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In /etc/sysconfig there is a comment

#
# Some broken implementations can't handle the RFC 1323 and RFC 1644
# TCP options.  If TCP connections randomly hang, try disabling this,
# and bug the vendor of the losing equipment.
#
tcp_extensions=YES

The only times I have found these connections to hang are in connecting 
to other FreeBSD boxes.  Last year, a particular 2.0.5 user could not 
exchange mail with me, and yesterday, a 2.1.5 user could not establish 
any TCP connections with any of my 2.0.5 or 2.1.5 machines.

In the incident last year, the other party turned off tcp extensions, and 
all worked.  This time, *I* turned off the extensions.  Question is: why 
is this only being seen between FreeBSD boxes?  I can quite happily talk 
amongst a network of around 10 FreeBSD machines with OS versions of 
2.0.5, 2.1.0R, 2.1.0-stable, 2.1.5R, but suddenly there is a FreeBSD 
2.1.5 machine I can't talk to. 

Does anyone have any ideas regarding what the other party or I have done 
wrong to wind up in this state.

If people would like to test out the other machine (still has extensions 
on, I believe) it is at pixel.planetx.com.au  - try telnetting to its 
smtp port.  One of my machines which has extensions on, and which won't 
talk to pixel, is tutu.schools.net.au.

If anyone can suggest a cause, I'm happy to attempt to do some debugging 
on this, if pointed in the right direction.

Danny



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