Computer Networks

Tutorial #10

1. What is the significance of the dot at the end of some domain names?

2. In the RR examples given in the lecture, the TTL field is set to 86400. What is the significance of this strange number?

3. What is meant by a "flat name space", and what is the alternative?

4. The DNS is described as a "distributed database" of RRs.
   1. What does this mean?
   2. What is the alternative, and why is it generally regarded as unworkable? Philosophical question: How does this alternative compare (conceptually) with the emergence of "search engine" sites such as Google and AltaVista for the World Wide Web?

5. Most implementations of 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?

6. Why^[1] should each nameserver know the IP address of its parent instead of the domain name of its parent?

7. What is a reverse lookup in the DNS, and why is it regarded as a significantly harder problem than normal lookups?

8. (Implementation question^[2]) 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?