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From: tcp-ip@ucbvax.ARPA
Newsgroups: fa.tcp-ip
Subject: Re: A Noop Strategy for TCP
Message-ID: <9514@ucbvax.ARPA>
Date: Wed, 31-Jul-85 15:27:05 EDT
Article-I.D.: ucbvax.9514
Posted: Wed Jul 31 15:27:05 1985
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From: David C. Plummer in disguise <DCP@SCRC-QUABBIN.ARPA>

Folks, we've been through this before, and there is the following large
comment in the TCP implementation I wrote for Symbolics:

	  ;; Very important note:  This does NOT, and is not intended to,
	  ;; ensure the other side of the connection is alive.  We are
	  ;; not asking for any positive confirmation that this ack was
	  ;; received.  What this IS for is to generate a RESET from the
	  ;; foreign host if the connection is known to be dead.  This
	  ;; issue was discussed on the TCP-IP@SRI-NIC mailing list from
	  ;; 22 Nov 83 and lasting for a few days.
	  ;; This mechanism is also used for the "zero window probe".
	  (send-ack-for-tcb tcb (get-tcp-segment tcb t) :idle-probe))