What Is DNS ??

The Domain Name System (DNS) is a
standard technology for managing the
names of Web sites and other Internet
domains. DNS technology allows you to
type names into your Web browser like
compnetworking.about.com and your
computer to automatically find that
address on the Internet. A key element of
the DNS is a worldwide collection of DNS
Server.
What Is a DNS Server?
A DNS server is any computer registered
to join the Domain Name System. A DNS
server runs special-purpose networking
software, features a public IP address, and
contains a database of network names and
addresses for other Internet hosts.
DNS Root Servers
DNS servers communicate with each other
using private network protocols. All DNS
servers are organized in a hierarchy. At
the top level of the hierarchy, so-called
root servers store the complete database
of Internet domain names and their
corresponding IP addresses. The Internet
employs 13 root servers that have become
somewhat famous for their special role.
Maintained by various independent
agencies, the servers are aptly named A, B,
C and so on up to M. Ten of these servers
reside in the United States, one in Japan,
one in London, UK and one in Stockholm,
Sweden.
DNS Server Hierarchy
The DNS is a distributed system, meaning
that only the 13 root servers contain the
complete database of domain names and
IP addresses. All other DNS servers are
installed at lower levels of the hierarchy
and maintain only certain pieces of the
overall database.
Most Lower level DNS servers are owned
by businesses or Internet Service Providers
(ISPs). For example, Google maintains
various DNS servers around the world that
manage the google.com, google.co.uk, and
other domains. Your ISP also maintains
DNS servers as part of your Internet
connection setup.
DNS networking is based on the client /
server architecture. Your Web browser
functions as a DNS client (also called DNS
resolver) and issues requests to your
Internet provider's DNS servers when
navigating between Web sites.
When a DNS server receives a request not
in its database (such as a geographically far
away or rarely visited Web site), it
temporarily transforms from a server to a
DNS client. The server automatically passes
that request to another DNS server or up
to the next higher level in the DNS
hierarchy as needed. Eventually the
request arrives at a server that has the
matching name and IP address in its
database (all the way to the root level if
necessary), and the response flows back
through the chain of DNS servers to your
client.
DNS Servers and Home Networking
Computers on your home network locate a
DNS server through the Internet
connection setup properties. Providers give
their customers the public IP address(es)
of primary and backup DNS servers. You
can find the current IP addresses of your
DNS server configuration via several
methods:
• on the configuration screens of a home
network router
• on the TCP/IP connection properties
screens in Windows Control Panel (if
configured via that method)
• from ipconfig or similar command line
utility
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