Learning Objectives

After successfully completing this section, you should be able to

  1. define the domain name system (DNS) and describe what it does.
  2. explain how DNS works and why it is important to the Internet.

Learning Tasks

Required:

  1. Watch the slideshow for this section.
  2. Study Section 2.4, DNS—The Internet’s Directory Service, in the textbook.

Terms and Topics

Section 4 – Domain Name System

DNS servers
Host aliasing
Canonical hostname
Mail server aliasing
Loading distribution among replicated servers
DNS design strategies
Problem with a centralized design
Single point of failure
Traffic volume
Distant centralized database
Maintenance of DNS servers
The hierarchy of Distributed DNS servers
Root DNS servers

Top-level domain (TLD) servers
Authoritative DNS servers
Local DNS server
Interaction of the various DNS servers
Recursive and iterative queries (to DNS servers)
DNS caching
DNS records and message
Resources Records (RRs)
Inserting records into DNS database
Registrar
ICANN

Leading Questions

  1. What is DNS? What is DNS used for?
  2. How does the Domain Name System work?
  3. Why is DNS so important for the Internet community?
  4. In DNS, what is host aliasing? Why is it needed?
  5. What is load distribution in DNS?
  6. What problems does a centralized DNS design have?
  7. Why is a distributed database important for DNS?
  8. What are root DNS servers? What roles do they play?
  9. What is a top-level domain (TLD) server?
  10. What are authoritative DNS servers?
  11. What are so-called local DNS servers?
  12. What are recursive queries and iterative queries in DNS?
  13. Why is DNS caching needed?
  14. What are resource records (RRs) in DNS? What is the format of resource record?
  15. What are DNS messages? What is the format?
  16. What can the nslookup command do for you?
  17. What roles does ICANN do?