Computing 205/406 & IT8

Tutorial #9

1. What is the domain name of the UNIX host you primarily use for electronic mail at LaTrobe, Bendigo? What is your email address?

2. Why is it considered important that the DNS is:
   1. Hierarchical?
   2. Distributed?

3. The domain name system allows abbreviations of names so that, for example, the name bindi resolves to a correct address at Bendigo. How is this handled by the nameserver? What about bindi.bendigo?

4. (Philosophical question) In the DNS, each nameserver is configured to know the IP address of its parent nameserver, rather than its name. Why is this very important? Is this advisable for ordinary hosts as well as nameservers?

5. (Implementation question) The standard suggests that when a program needs to find the domain name associated with an IP address, it should send an inverse query to the local server first and domain in-addr.arpa only if that fails. Why?

6. (Research question - very difficult) Read the DNS standards and find out how the domain name system uses SOA records.

Practical exercises:

• Use the nslookup or dig utilities to investigate domain names. Within nslookup, type h for help and take it from there. Try typing bindi.bendigo.latrobe.edu.au and bindi.bendigo.latrobe.edu.au. (ie, with a trailing dot). Try just bindi on its own, and bindi.bendigo Interesting? Use exit or ^D to get out of nslookup. Try set query=CNAME, or a few other RR types, then repeat the exercise.
• Some of the WWW "search engines" are getting pretty good at finding people on the net. Try using one of these (eg, Lycos, Web Crawler, Alta Vista) to find someone you know.