WHAT IS DNS SERVER
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 servers
. What, then, 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
, and contains a database of network names and addresses for other
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
- on the TCP/IP connection properties screens in Windows Control Panel (if
configured via that method)
- from ipconfig or similar command line utility