I know that UDP has no real error control facilties outside of silent discard of packets failing checksums.
Am I correct in thinking that a UDP packet with a TTL=1 reaching a router will generate an ICMP Time Exceeded message, and a UDP packet arriving with an unused port # (54823 or something) at an end host will be rejected, causing an ICMP Port Unreachable message - and that both of those ICMP messages would be sent back to the originator of the message?
I'm pretty sure that's how it works, but I wanted to make sure I wasn't confusing myself somehow