User Manual

Chapter 12 Configuring DNS 55
About the Domain Name System
This section discusses key concepts of the domain name system.
Purpose of DNS
The domain name system maps domain names to information associated
with these names, such as IP addresses.
DNS Components
DNS components include:
• A distributed database consisting of domain names and associated
information
• A hierarchical system of domain name servers that maintain the
database and use it to respond to requests for information about a
particular domain name, such as its IP address
• Domain name resolvers that
— Accept requests from users
— Satisfy information requests by building and submitting properly
formulated queries to one or more name servers or by retrieving
information from a local host file
— Return information to users
— Cache information for future use
Types of Name Servers
There are two types of name servers in the domain name system:
• Local servers maintain information for resources within a local zone.
It is up to individual network administrators to determine the scope
of a local zone.
• Root servers maintain information in higher-level domains than do
local servers.
Typically, when a user requires information about a domain name, the
resolver queries a local server. If local servers cannot provide the
information, root servers are queried next.
Naming Conventions
Each node in the domain name system has a globally unique domain name
that consists of its own name, which is called a label, and the labels of all
superior nodes.
DNS Name Example
Here is an example of a domain name. Note that labels are separated by
Chapter 12
Configuring DNS