david@l8s.co.uk (David Laight) writes:
> If that why traceroute uses UDP datagrams rather than the
> (apparantly more obvious) ICMP echo packets?
> 
> If routers decrement the ttl of icmp echo packets, maybe
> traceroute should default to icmp - makeing firewall
> configuration that much easier...

There was also a bit of confusion in the RFC about hosts and routers
being allowed to send ICMP error messages in response to incoming ICMP
messages.  Some IP authors took the prohibition very literally and
never sent any ICMP error messages in response to ICMP messages.

Lately most folks are just interpreting the ICMP prohibition to mean
you can't send ICMP error messages in reply to other ICMP error
messages.

-wolfgang
-- 
       Wolfgang Rupprecht <wolfgang+gnus@dailyplanet.wsrcc.com>
		    http://www.wsrcc.com/wolfgang/
Coming soon: GPS mapping tools for Open Systems. http://www.gnomad-mapping.com/