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Date:      Mon, 21 Mar 2005 12:21:41 -0500
From:      Charles Swiger <cswiger@mac.com>
To:        Robert Gogolok <robertgogolok@web.de>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: FIN_WAIT_2
Message-ID:  <56b90b3668acea792519e1e70a7b837a@mac.com>
In-Reply-To: <423EFE41.6040805@web.de>
References:  <423EFE41.6040805@web.de>

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On Mar 21, 2005, at 12:02 PM, Robert Gogolok wrote:
> The webserver is running FreeBSD, and currently I get many FIN_WAIT_2 
> states:
> # netstat -n -p tcp | grep FIN_WAIT_2 | wc -l
> 48
>
> I wonder WHAT is responsible for sending every 5 minutes ACK messages 
> to the clients in FIN_WAIT_2 state?  tcp.inet.tcp.always_keepalive 
> seems to be something else

The TCP stack wants the remote end to acknowledge the last FIN it sends 
and close the connection cleanly, and there is a timer (2 * MSL?) which 
gets started when a connection moves into the closing stages 
(FIN_WAIT_1, FIN_WAIT_2, LAST_ACK).

It's not uncommon for some clients (think dialup users running Win98), 
to drop the connection rather rather than close it properly.  Your 
system should time out these connections after a while.

-- 
-Chuck



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