I guess this means that providers who utilize rfc1918 along their hops
should make an effort to ensure these addresses are not used for icmp
messages or translate these addresses when they source icmp.
TTL-E messages _do_ have legitimate function in network management.
TTL-E messages _can_ originate from RFC1918 space, addressed to 'public
internet' addresses. Usefully, and meaningfully. Ever hear of 'traceroute'?
Ever use it where packets went across a network using RFC1918 internally?
Ever had a route die _between_ two RFC1918 addressed nodes on somebody elses