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From: THARENOS@IBM.COM.UUCP
Newsgroups: mod.protocols.tcp-ip
Subject: FIN-WAIT-2 to TIME-WAIT transition
Message-ID: <021787.121742.tharenos@ibm.com>
Date: Tue, 17-Feb-87 20:06:19 EST
Article-I.D.: ibm.021787.121742.tharenos
Posted: Tue Feb 17 20:06:19 1987
Date-Received: Wed, 18-Feb-87 22:19:45 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
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Approved: tcp-ip@sri-nic.arpa

> The question is, what is a TCP to do if it is in FIN-WAIT-2, it has some
> user data that the user hasn't asked for yet, and a FIN comes in?  If it
> goes immediately to TIME-WAIT (as this TCP does) the user will receive an error
> because RFC 793 says that a RECEIVE call while in TIME-WAIT returns "error:

   Thought I'd take a stab at this one .... The key here is that a FIN implies
a PUSH.   It is the responsibility of your TCP to asyncronously notify the
client that a PUSH has arrived and that a RECEIVE is needed.  If the client is
well behaved, then a RECEIVE should be forthcoming.  However, this is where
your question gets tricky.  Should TCP wait before entering the TIME-WAIT
state for the client to respond with the receive?  This adds a client condition
to the state table of TCP.  If the client was smarter, there would be multiple
RECEIVEs queued and TCP could satisfy the FIN(push) immediately and thus
enter TIME-WAIT without worry.  If, however, your client decides to be a bad
client and wait a few hours before issuing the RECEIVE, then your question
comes to light.  I would venture a guess that TCP should stay in FIN-WAIT-2
until the push signal has been satisfied with a RECEIVE and then enter
TIME-WAIT.

Mike Tharenos <Tharenos@ibm.COM>
Networking Support and Development
IBM, Almaden Research Center
408-927-2727