DNS





The Domain Name System, most often known as simply DNS, is a core feature of
the Internet. It is a distributed database that handles the mapping between
host names (domain names), which are more convenient for humans, and the
numerical Internet addresses. That is, it acts much like a phone book, so
you can "call" www.wikipedia.org instead of 130.94.122.199.

DNS was first invented in 1983 by Paul Mockapetris; the original
specifications are described in RFC 882. In 1987 RFC 1034 and RFC 1035 were
published which updated the DNS specifcation and made RFC 882 and RFC 883
obsolete. Subsequent to that there have been quite a few RFCs published that
propose various extensions to the core protocols.

DNS implements a hierarchical name space by allowing name service for parts
of a name space known as zones to be "delegated" by a name server to
subsidiary name-servers. DNS also provides additional information, such as
alias names for systems, contact information, and which hosts act as mail
hubs for groups of systems or domains.

The DNS system is run by various flavors of DNS software, including:

   * BIND (Berkeley Internet Name Domain), the most commonly used
     namedaemon.
   * DJBDNS (Dan J Bernstein's DNS implementation)
   * MaraDNS
   * NSD (Name Server Daemon)

Any IP computer network can use DNS to implement its own private name
system. However, the term "domain name" is most commonly used to refer to
domain names implemented in the public Internet DNS system. This is based on
thirteen "root servers" worldwide, all but three of which are in the United
States of America. From these thirteen root servers, the rest of the
Internet DNS name space is delegated to other DNS servers which serve names
within specific parts of the DNS name space.

An owner of a domain name can be found by looking in the whois database,
which is generally maintained by domain registrars.

The current way the main DNS system is controlled is often criticized. The
most common problems pointed at are that it is abused by monopolies or
near-monopolies such as VeriSign Inc., and problems with assignment of
top-level domains. Some also allege that many implementations of DNS server
software fail to work gracefully with dynamically allocated IP addresses,
although that is the failure of specific implementations and not failures of
the protocol itself.

DNS uses TCP and UDP ports 53.