Exercises

17.1	We've covered the following packet formats, each of which has a checksum in its corresponding header: IP, ICMP, IGMP, UDP, and TCP. For each one, describe what portion of an IP datagram the checksum covers and whether the checksum is mandatory or optional.
17.2	Why do all the Internet protocols that we've discussed (IP, ICMP, IGMP, UDP, TCP) quietly discard a packet that arrives with a checksum error?
17.3	TCP provides a byte-stream service where record boundaries are not maintained between the sender and receiver. How can applications provide their own record markers?
17.4	Why are the source and destination port numbers at the beginning of the TCP header?
17.5	Why does the TCP header have a header length field while the UDP header (Figure 11.2) does not?