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FIN_WAIT_2 and TIME_WAIT

From:
Benjamin Franks
Date:
December 10, 2001 15:10
Subject:
FIN_WAIT_2 and TIME_WAIT
Message ID:
20011210231017.0489836F9@sitemail.everyone.net
Last week I sent a message to the group asking about a particular high number of FIN_WAIT_2 states in my client netstat output.  I had written both an http client application (using LWP::UserAgent) and http server application (using IO::Socket) that were communicating with one another.  Just out of interest and for the sake of testing, I've done a number of things which seem to result in fewer FIN_WAIT_2 states:

(1) change the http server application to use HTTP::Daemon and use the $c->force_last_request method.  The server is still closing the connection after sending out a little bit of information.
(2) include a "Connection: close" header in the client's request.
(3) change the sysctl variable net.inet.tcp.always_keepalive to false rather than the default behavior of true.

First of all, are any of these changes not advisable?

I've also noticed that there seems to be a higher likelihood of hanging in a FIN_WAIT_2 state when the client to server connection is made through a proxy?  Is there a general reason this would be the case?  Would proxies be attempting to keepalive tcp connections to client/server while the client/server had closed them or attempted to?

I'd like to now decrease the amount of time the server side stays in the TIME_WAIT state.  I know that the FIN_WAIT_2 is the last normal state for the client side and the TIME_WAIT is the last normal state for the server side and their lifetime exists for a reason.  However, are there things I can do to decrease the TIME_WAIT lifetime?

Thanks,
--Ben


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