From: van@ee.lbl.gov (Van Jacobson)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: traceroute history: why UDP?
Date: 8 Feb 1999 08:36:20 GMT
Organization: Lawrence Berkeley National Laboratory, Berkeley CA
Message-ID: <79m7m4$reh$1@dog.ee.lbl.gov>
References: <79lub9$8e81@oberon.sweden.hp.com>

In article <79lub9$8e81@oberon.sweden.hp.com>,
	stevesk@sweden.hp.com (Kevin Steves) writes:
> Were ICMP probes considered in 1988 when Van wrote traceroute?

The very first traceroute (never released) used icmp echo.  RFC792 (the
icmp spec) contains the words:

   The ICMP messages typically report errors in the processing of
   datagrams.  To avoid the infinite regress of messages about messages
   etc., no ICMP messages are sent about ICMP messages.

During the first night of testing I found that more than half the
router vendors of the time had taken this at face value & would not
return an ICMP Time Exceeded for an ICMP Echo.  That's when I changed
to UDP.

 - Van