::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. Most prominently, it translates domain names, which can be easily memorized by humans, to the numerical IP addresses needed for the purpose of computer services and devices worldwide. The Domain Name System is an essential component of the functionality of most Internet services because it is the Internet's primary directory service.

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 supported domains, and may delegate authority over sub-domains to other name servers. This mechanism provides distributed and fault tolerant service and was designed to avoid the need for a single central database.

The Domain Name System also specifies the technical functionality of the database service which is at its core. It defines the DNS protocol, a detailed specification of the data structures and data communication exchanges used in DNS, as part of the Internet Protocol Suite. Historically, other directory services preceding DNS were not scalable to large or global directories as they were originally based on text files, prominently the HOSTS.TXT resolver. DNS has been in wide use since the 1980s.

The Internet maintains two principal namespaces, the domain name hierarchy<ref name=rfc1034>RFC 1034, Domain Names - Concepts and Facilities, P. Mockapetris, The Internet Society (November 1987)</ref> and the Internet Protocol (IP) address spaces.<ref name="rfc781">RFC 781, Internet Protocol - DARPA Internet Program Protocol Specification, Information Sciences Institute, J. Postel (Ed.), The Internet Society (September 1981)</ref> 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.<ref name=rfc1035>RFC 1035, Domain Names - Implementation and Specification, P. Mockapetris, The Internet Society (November 1987)</ref> A DNS name server is a server that stores the DNS records for a domain name; a DNS name server responds with answers to queries against its database.

The most common types of records stored in the DNS database are for DNS zone authority (SOA), IP addresses (A and AAAA), SMTP mail exchangers (MX), name servers (NS), pointers for reverse DNS lookups (PTR), and domain name aliases (CNAME). Although not intended to be a general purpose database, DNS can store records for other types of data for either automatic machine lookups, such as DNSSEC records, or for human queries such as responsible person (RP) records. As a general purpose database, DNS has also seen use in combating unsolicited email (spam) by using a real-time blackhole list stored in the DNS. Whether for Internet naming or for general purpose uses, the DNS database is traditionally stored in a structured zone file.

Domain Name System sections
Intro  Function  History  [[Domain_Name_System?section=Structure_{{safesubst:#invoke:anchor|main}}|Structure {{safesubst:#invoke:anchor|main}}]]  Operation  DNS message format  Protocol transport  DNS resource records  Protocol extensions  Dynamic zone updates  Security issues  Domain name registration  Internet standards  See also  References  External links  

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