Path: utzoo!attcan!uunet!lll-winken!ames!pasteur!ucbvax!UC.MSC.UMN.EDU!slevy
From: slevy@UC.MSC.UMN.EDU ("Stuart Levy")
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  connection between ARP and ICMP...
Message-ID: <8901071437.AA21764@uc.msc.umn.edu>
Date: 7 Jan 89 13:37:48 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 13

A year or so ago on this list, someone suggested that "Host Unreachable"
should be returned when there was no response after some number of ARP
retries.  On a network where there's no direct indication that a packet
was received, this seems as good a method as any to detect dead hosts.
I don't believe it would be a layering violation, any more than translating
ARPAnet "Host Dead" status into "Host Unreachable" is -- it's just implementing
a well-defined network layer service.

On the other hand, to send "Host Unreachable" immediately just because there's
no ARP response in the cache is clearly broken.  It should make some attempt
to contact the host before saying this.

	Stuart Levy