Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!pur-ee!mentor.cc.purdue.edu!dls
From: dls@mentor.cc.purdue.edu (David L Stevens)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: TCP Protocol Question: reusing connections
Keywords: SYN, RST, Connection Establishment
Message-ID: <8020@mentor.cc.purdue.edu>
Date: 1 Mar 90 03:59:33 GMT
References: <1125@devildog.UUCP>
Reply-To: dls@mentor.cc.purdue.edu (David L Stevens)
Distribution: usa
Organization: PUCC UNIX Group
Lines: 16


	You get the RST from MachineB because it has to wait 2MSL (TIME_WAIT
state in the TCP spec) to make sure that MachineA's idea of that connection has
died. If MachineB gets anything else with the same port pair, it assumes it's
a retransmission (normally) and ACK's it. Unfortunately, SYN is only allowed
when MachineB's end is in LISTEN, but it's in TIME_WAIT. Ooops => RST.
	You'd get the RST regardless of the sequence numbers, though you'd
get one for ACKing more than MachineB sent, if that were the case, too. The
window management really isn't related though-- the problem is that MachineB
can't be sure that MachineA got his ACK of A's FIN, so it has to wait around
to handle retransmissions gracefully.

	It's doing the right thing and the solution is to have one of them
pick a different port each time.
-- 
					+-DLS  (dls@mentor.cc.purdue.edu)