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From: PADLIPSKY@A.ISI.EDU (Michael Padlipsky)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: ..."layering violations"
Message-ID: <12347435144.54.PADLIPSKY@A.ISI.EDU>
Date: Mon, 2-Nov-87 12:27:00 EST
Article-I.D.: A.12347435144.54.PADLIPSKY
Posted: Mon Nov  2 12:27:00 1987
Date-Received: Fri, 6-Nov-87 22:48:21 EST
References: <1505@faline.bellcore.com>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 23

Phil--
   A sidelight on keeping connections open "forever" seems appropriate,
just in case anybody doesn't attach enough strength to the quotation
marks you rightly used:  In the early days of the Multics "NCP" [sic],
we discovered that we were sending "RST"s (the old Host-Host Protocol
Reset command, which was sent whenever an NCP came back up, to "everybody"
--well, you could do that sort of thing when there weren't four dozen
Hosts in the world) without end to a particular Host.  It turned out the
problem was that we were getting "Incomplete Transmission" from our IMP,
so we tried again, since that code was supposed to mean that a temporary
problem had prevented successful transmission; however, the Host in
question had somehow jumpered their IMP interface in such a fashion as
to convince their IMP that they really were up when they weren't and so
we got the code in a circumstance where we really shouldn't have.
Naturally, we put a limit on the retransmisions after an Incomplete
Transmission was encountered after that (and we probably should have
had one in the first place).  The moral does seem worth pointing out,
though: keep connections open for appropriately small values of forever.
(For example, if you happen to get a Host Down, you might as well close
even if you're only a daemon, since the other side should come up again
out of Sequence Number synch--shouldn't it?)
   cheers, map
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