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Internetworking with TCP/IP: Pearson New International Edition

Douglas E. Comer

Chapter 23

The Domain Name System (DNS) - all with Video Answers

Educators

Chapter Questions

Problem 1

The name of a computer should never be bound into an operating system at compile time. Explain why.

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Problem 2

Would you prefer to use a computer that obtained its name from a remote file or from a configuration server? Why?

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Problem 3

Why does each name server know the IP address of its parent instead of the domain name of its parent?

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02:14

Problem 4

Devise a naming scheme that tolerates changes to the naming hierarchy. As an example, consider two large companies that each have an independent naming hierarchy, and suppose the companies merge. Can you arrange to have all previous names still work correctly?

Florencia Cuzmar
Florencia Cuzmar
Numerade Educator

Problem 5

Read the standard and find out how the Domain Name System uses SOA records. What is the motivation for $S O A$ ?

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Problem 6

The Internet Domain Name System can also accommodate mailbox names. Find out how.

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Problem 7

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 use domain in-addr .arpa or ip6.arpa only if that fails. Why?

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Problem 8

How would you accommodate abbreviations in a domain naming scheme? As an example, show two sites that are both registered under .edu and a top level server. Explain how each site would treat each type of abbreviation.

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Problem 9

Obtain the official description of the Domain Name System and build a client program. Look up the name xinu.cs.purdue.edu.

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01:38

Problem 10

Extend the exercise above to include a pointer query. Try looking up the domain name for address $128 \cdot 10 \cdot 19 \cdot 20$.

Adriano Chikande
Adriano Chikande
Numerade Educator
01:22

Problem 11

Find a copy of the dig application, and use it to look up the names in the two previous exercises.

AG
Ankit Gupta
Numerade Educator
08:14

Problem 12

If we extended the domain name syntax to include a dot after the top-level domain, names and abbreviations would be unambiguous. What are the advantages and disadvantages of the extension?

Caroline Jones
Caroline Jones
Numerade Educator

Problem 13

Read the RFCs on the Domain Name System. What are the maximum and minimum possible values a DNS server can store in the TIME-TO-LIVE field of a resource record? What is the motivation for the choices?

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Problem 14

Should the Domain Name System permit partial match queries (i.e., a wildcard as part of a name)? Why or why not?

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Problem 15

The Computer Science department at Purdue University chose to place the following type $A$ resource record entry in its domain name server:
localhost.cs.purdue.edu 127.0.0.1
Explain what will happen if a remote site tries to ping a machine with domain name localhost.cs.purdue.edu.

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