Domain Name
System
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The Domain Name System (DNS) is a hierarchical
distributed 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
participating entities. A Domain
Name Service resolves queries
for these names into IP addresses for the purpose of locating computer services
and devices worldwide. By providing a worldwide, distributed keyword-based
redirection service, the Domain Name System is an essential component of the
functionality of the Internet.
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, the domain name www.example.com translates to the addresses 192.0.43.10 (IPv4) and 2620:0:2d0:200::10 (IPv6). Unlike a phone
book, however, DNS can be quickly updated and these updates distributed,
allowing a service's location on the network to change without affecting the
end users, who continue to use the same hostname. Users take advantage of this
when they recite meaningful Uniform Resource Locators (URLs) and e-mail
addresses without having to
know how the computer actually locates the services.
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.
Additionally, the responsibility for maintaining and updating the master record
for the domains is spread among many domain name registrars, who compete for
the end-user's, domain-owner's, business. Domains can be moved from registrar
to registrar at any time.
The Domain Name
System also specifies the technical functionality of this database service. 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.
The Internet
maintains two principal namespaces,
the domain name hierarchy[1] and the Internet
Protocol (IP) address spaces.[2] The Domain Name System maintains the
domain name hierarchy and provides translation services between it and the
address spaces. Internet name servers and a communication protocol implement the Domain Name System.[3] A DNS name server is a server that
stores the DNS records for a domain name, such as address (A) records, name
server (NS) records, and mail exchanger (MX) records (see also list of DNS record types); a DNS name
server responds with answers to queries against its database.
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