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From: minshall@OPAL.BERKELEY.EDU
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Are simultaneous TCP opens useful?
Message-ID: <8709021539.AA22092@opal.berkeley.edu>
Date: Wed, 2-Sep-87 11:39:47 EDT
Article-I.D.: opal.8709021539.AA22092
Posted: Wed Sep  2 11:39:47 1987
Date-Received: Sat, 5-Sep-87 06:14:53 EDT
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Eric,
	Whether "simultaneous" opens will always succeed or randomly
fail depends on how the underlying TCP service is implemented.  If
the user code needs to look like this:
	{
	    if (connect() == FAIL) {
		listen();
	    }
	}
	then there is a race condition in which both sides may hang
in listen().  Side A fails to connect, but before A issues listen, side
B tries to connect and fails.

	However, if the underlying TCP service allows this:
	{
	    connect_or_listen();
	}
	as a primitive, then the simultaneous case seems to me to be
guaranteed to win.  Note that I don't know of any underlying services
that allow the second form.

Greg Minshall