Exercises

6.1	At the end of Section 6.2 we listed five special conditions under which an ICMP error message is not sent. What would happen if these five conditions weren't followed and we sent a broadcast UDP datagram to an unlikely port on the local cable?
6.2	Read the Host Requirements RFC [Braden 1989a] to see if the generation of an ICMP port unreachable is a "must," "should," or "may." What section and page is this found on?
6.3	Read RFC 1349 [Almquist 1992] to see how the IP type-of-service field (Figure 3.2) should be set by ICMP.
6.4	If your system provides the `netstat` command, use it to see what types of ICMP messages are received and sent.