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From: tai%hpltyj@HPLABS.HP.COM (Tai Jin)
Newsgroups: comp.protocols.tcp-ip
Subject: ICMP echo
Message-ID: <8704242338.AA01718@hpltyj>
Date: Fri, 24-Apr-87 18:38:31 EDT
Article-I.D.: hpltyj.8704242338.AA01718
Posted: Fri Apr 24 18:38:31 1987
Date-Received: Tue, 28-Apr-87 02:52:52 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 10

I have a question for those experienced in using ICMP echo for
debugging.  Does the spec specify how a system is supposed to reply to
an echo?

One implementation is to turn around and send the reply to the link
address of the sender (or gateway).  The other is to make a local
routing decision before sending the reply.  Which is better?

Another question is whether a system should reply to an ICMP echo sent
to a broadcast address.