Exercises

14.1	Classify a DNS resolver and a DNS name server as either client, server, or both.
14.2	Account for all 75 bytes in the response in Figure 14.12 .
14.3	In Section 12.3 we said that an application that accepts either a dotted -decimal IP address or a hostname should assume the former, and if that fails, then assume a hostname. What happens if the order of the tests is reversed ?
14.4	Every UDP datagram has an associated length. A process that receives a UDP datagram is told what its length is. When a resolver issues a query using TCP instead of UDP, since TCP is a stream of bytes without any record markers, how does the application know how much data is returned? Notice that there is no length field in the DNS header (Figure 14.3). ( Hint: Look at RFC 1035.)
14.5	We said that a name server must know the IP addresses of the root servers and that this information is available via anonymous FTP. Unfortunately not all system administrators update their DNS files whenever changes are made to the list of root servers. (Changes do occur to the list of root servers, but not frequently.) How do you think the DNS handles this?
14.6	Fetch the file specified in Exercise 1.8 and determine who is responsible for maintaining the root name servers. How frequently are the root servers updated?
14.7	What is a problem with maintaining the cache in the name server, and having a stateless resolver?
14.8	In the discussion of Figure 14.10 we said that the name server sorts the A records so that addresses on common networks appear first. Who should sort the A records, the name server or the resolver?