For each of the following ICMP messages, list their possible senders (routers, non-destination hosts, and destination hosts).
a) Type: destination unreachable,
Code: 2 protocol
Code: 3 port is unreachable
b) Type: source quench,
Code: 0
c) Type: time exceeded,
Code: 1 (note: when the final destination does not receive all of the fragments in a set time, it discards the received fragments and sends a time-exceeded message (code 1) to the original source)
d) Type: Redirection,
Code: 1 redirect to a host-specific route