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From: smb@ulysses.UUCP (Steven Bellovin)
Newsgroups: mod.protocols.tcp-ip
Subject: Re:  SMTP, 2600, and the security of mail
Message-ID: <8609302056.AA03119@nestor.UUCP>
Date: Tue, 30-Sep-86 16:56:58 EDT
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Posted: Tue Sep 30 16:56:58 1986
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It's important to remember that SMTP is used on non-TCP virtual circuits.
For example, some hosts within Bell Labs use it over Datakit(r) VCS connections.
You can't do this nearly as easily with FTP because the semantics of some of
the commands (i.e., PORT and PASSIVE) are intimately tied to TCP and IP.  In
general, though, I regard SMTP as a newer and better protocol than FTP, and
as a better model for other protocols.  The concept of looking for the initial
state is a good one; I've often seen half-open circuits get spliced to due
to software bugs (though not on TCP, of course).