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From: tcp-ip@ucbvax.ARPA
Newsgroups: fa.tcp-ip
Subject: Re: A Noop Strategy for TCP - second level comments.
Message-ID: <9475@ucbvax.ARPA>
Date: Tue, 30-Jul-85 01:16:58 EDT
Article-I.D.: ucbvax.9475
Posted: Tue Jul 30 01:16:58 1985
Date-Received: Thu, 1-Aug-85 06:34:08 EDT
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Organization: University of California at Berkeley
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From: geof@su-shasta.arpa


Actually, a telnet SERVER is an example of an unmonitored network
service.  Class #3 was the number in my listing, I believe.  I left it
out of my examples because the telnet protocol has higher-level probing
in the form of NOOP negotiations.  Few telnet server programs actually
exercise this option, though.  Interpret my last message as a harangue
at them and other server implementations of this class.

When I see idle network connections on the system, I exercise them (and
exorcise them) by sending a terminal message to the idle user which
says "are you still there".  The negative response is that the user's
TCP connection times out (or -- usually -- gets reset) and the spurious
login goes away.  I guess a quick fix for a harried system
administrator who doesn't want to hack code (or can't -- not everyone
has sources these days) is to use /etc/cron to run a program once every
hour or so that just sends a useless message to every network login.  I
guess that you could send a "^A" or something that would tend not to be
visible, except for messing up an Emacs screen occasionally.

- Geof