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Path: utzoo!utgpu!water!watmath!clyde!rutgers!ucla-cs!zen!ucbvax!ACC-SB-UNIX.ARPA!kzm
From: kzm@ACC-SB-UNIX.ARPA.UUCP
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Are simultaneous TCP opens useful?
Message-ID: <8709022110.AA29315@ACC-SB-UNIX.ARPA>
Date: Wed, 2-Sep-87 17:10:44 EDT
Article-I.D.: ACC-SB-U.8709022110.AA29315
Posted: Wed Sep  2 17:10:44 1987
Date-Received: Fri, 4-Sep-87 03:16:56 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
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As Art Berggreen said in an earlier message, ACC has a product called
SIMON which provides a TCP-based service for peer subscribers (as
opposed to the more common Client/Server model).  

Several years ago when we were implementing this, we needed a scheme 
which avoided the race condition which Greg Minshall pointed out.  So, 
we asked Jon Postel about the validity of using the primitive which 
Greg calls "connect_or_listen", which we call a "symmetric" (as opposed 
to passive or active) open.  Jon said if we wanted to enhance our ULP 
interface like this, then fine.  This single primitive requests an
active open with an "automatic" fallback to passive if the active fails.
When both subscribers use this primitive, the ability to fallback
immediately eliminates the race condition.

Keith.