The
Domain Name System (
DNS) is a
distributed hierarchical naming system for computers, services, or any resource connected to the
Internet or a
private network. It associates various information with
domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to
humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide. An often-used analogy to explain the Domain Name System is that it serves as the "
phone book" for the Internet by translating human-friendly computer
hostnames into
IP addresses. For example,
www.example.com translates to the addresses
192.0.32.10 (IPv4) and
2620:0:2d0:200::10 (IPv6).
The Domain Name System makes it possible to assign
domain names to groups of Internet users in a meaningful way, independent of each user's physical location. Because of this,
World Wide Web (WWW)
hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device. Internet domain names are easier to remember than IP addresses such as
208.77.188.166 (
IPv4) or
2001:db8:1f70::999:de8:7648:6e8 (
IPv6). People take advantage of this when they recite meaningful
URLs and
e-mail addresses without having to know how the machine will actually locate them.
The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating
authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed and fault tolerant and has helped avoid the need for a single central register to be continually consulted and updated.
In general, the Domain Name System also stores other types of information, such as the list of
mail servers that accept
email for a given Internet domain. By providing a worldwide, distributed
keyword-based redirection service, the Domain Name System is an essential component of the functionality of the
Internet.
Other identifiers such as
RFID tags,
UPC codes, International characters in email addresses and host names, and a variety of other identifiers could all potentially utilize DNS.
The Domain Name System also defines the technical underpinnings of the functionality of this database service. For this purpose it defines the DNS protocol, a detailed specification of the data structures and communication exchanges used in DNS, as part of the
Internet Protocol Suite (TCP/IP).
