Domain
Names
The
address that is used at the computer level to uniquely identify a
specific computer on the Internet is called the Internet Protocol
(IP) address. An IP address consists of four sets of numbers,
separated by periods, for example: 131.107.1.7 or 131.107.1.240.
Although a computer application has no difficulty with this
numerical addressing system, people find it easier to remember
user-friendly domain names, such as example.microsoft.com. However,
before a computer can
connect to the Internet, its domain name must be mapped, or
resolved, to a unique IP address. A classification system called the
Domain Name System (DNS) maps domain names to IP addresses. When you
use a domain name to connect to a computer on the Internet, a DNS
server resolves the name to an IP address. The server uses the
mapping to locate the target computer’s IP address and substitute it
for the user-friendly name to connect to the computer on the
Internet.
DNS
uniquely identifies computers connected to the Internet based on a
hierarchy that includes a top-level domain, a second-level domain,
and often one or more subdomains. The top-level domain is based
either on generic codes or country codes. Generic top-level domains
indicate the type of organization. This table lists the generic
top-level domains and their corresponding organizations.
|
Generic code |
Description |
|
com |
Commercial organizations |
|
edu |
Educational institutions |
|
gov |
Government agencies |
|
int |
International associations |
|
mil |
Military organizations |
|
net |
Major network support centers |
|
org |
Other organizations |
Country code top-level domains are two-letter codes, such as US for
the United States and CA for Canada.
The
second-level domain represents the name of a company, institution,
or organization and is separated from the top-level domain by
a period (called “dot”). An example of a second-level domain is
microsoft.com. An individual or a small company typically use one
domain name and one IP address, but large companies often acquire a
block of IP addresses and establish subdomains. For example,
microsoft.com is a domain name, and
examle.microsoft.com is a subdomain of the main Microsoft domain.
The Internet Corporation for Assigned Names and Numbers (ICANN)
manages the assignment of domain names.
