| 21.1 | Build the program shown in Figure 20.9 and run it specifying an IP address on the command line of 224.0.0.1. What happens? |
| 21.2 | Modify the program in the previous example to bind 224.0.0.1 and port 0 to its socket. Run it. Are you allowed to bind a multicast address to the socket? If you have a tool such as tcpdump, watch the packets on the network. What is the source IP address of the datagram you send? |
| 21.3 | One way to tell which hosts on your subnet are multicast-capable is to ping the all-hosts group: 224.0.0.1. Try this. |
| 21.4 | One way to tell if your host is connected to the IP multicast infrastructure is to run our program from Section 21.9, wait a few minutes, and see if any session announcements appear. Try this and see if you receive any announcements. |
| 21.5 | Go through the calculations in Figure 21.22 when the fractional part of the NTP timestamp is 1,073,741,824 (one-quarter of 232).
Redo these calculations for the largest possible integer fraction (232 – 1). |
| 21.6 | Modify the implementation of mcast_set_if for IPv4 to remember each interface name for which it obtains the IP address to prevent calling ioctl again for that interface. |
