.arpa
Encyclopedia
The domain name arpa is a top-level domain
(TLD) in the Domain Name System
of the Internet
. It is used exclusively for technical infrastructure purposes. While the name originally was the acronym for the Advanced Research Projects Agency (ARPA), the funding organization in the United States that developed the precursor of the Internet (ARPANET
), it now stands for
Address and Routing Parameter Area.
arpa contains also the domains for reverse domain name resolution in-addr.arpa and ip6.arpa for IPv4
and IPv6
, respectively.
(DNS). It was originally intended to be a temporary domain to facilitate the transition of the ARPANET host naming conventions and the host table distribution methods to the Domain Name System. The ARPANET was the predecessor to the Internet, established by the United States Department of Defense
Advanced Research Projects Agency (DARPA). When the Domain Name System was introduced in 1985, ARPANET host names were initially converted to domain names by adding the arpa domain name label to the end of the existing host name, separated with a full stop
. Domain names of this form were subsequently rapidly phased out by replacing them with domain names under the newly introduced, categorized top-level domains.
After arpa had served its transitional purpose, it proved impractical to remove the domain, because in-addr.arpa was used for reverse DNS lookup
of IP address
es. For example, the mapping of the IP address 145.97.39.155 to a host name is obtained by issuing a DNS query for a pointer record of the domain name 155.39.97.145.in-addr.arpa.
It was intended that new infrastructure databases would be created in the top-level domain int
. However, in May 2000 this policy was reversed, and it was decided that arpa should be retained for this purpose, and int should be used solely by international organizations. In accordance with this new policy, arpa now officially stands for Address and Routing Parameter Area (a backronym
).
Beginning in March 2010 the arpa zone is signed (DNSSEC
).
Top-level domain
A top-level domain is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a...
(TLD) in the Domain Name System
Domain name system
The Domain Name System 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...
of the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
. It is used exclusively for technical infrastructure purposes. While the name originally was the acronym for the Advanced Research Projects Agency (ARPA), the funding organization in the United States that developed the precursor of the Internet (ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
), it now stands for
Backronym
A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....
Address and Routing Parameter Area.
arpa contains also the domains for reverse domain name resolution in-addr.arpa and ip6.arpa for IPv4
IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
and IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
, respectively.
History
The arpa top-level domain was the first domain installed in the Domain Name SystemDomain name system
The Domain Name System 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...
(DNS). It was originally intended to be a temporary domain to facilitate the transition of the ARPANET host naming conventions and the host table distribution methods to the Domain Name System. The ARPANET was the predecessor to the Internet, established by the United States Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...
Advanced Research Projects Agency (DARPA). When the Domain Name System was introduced in 1985, ARPANET host names were initially converted to domain names by adding the arpa domain name label to the end of the existing host name, separated with a full stop
Full stop
A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people...
. Domain names of this form were subsequently rapidly phased out by replacing them with domain names under the newly introduced, categorized top-level domains.
After arpa had served its transitional purpose, it proved impractical to remove the domain, because in-addr.arpa was used for reverse DNS lookup
Reverse DNS lookup
In computer networking, reverse DNS lookup or reverse DNS resolution is the determination of a domain name that is associated with a given IP address using the Domain Name System of the Internet....
of IP address
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
es. For example, the mapping of the IP address 145.97.39.155 to a host name is obtained by issuing a DNS query for a pointer record of the domain name 155.39.97.145.in-addr.arpa.
It was intended that new infrastructure databases would be created in the top-level domain int
.int
The domain name int is a sponsored top-level domain in the Domain Name System of the Internet. Its name is derived from the word international, characterizing its use for world-wide purposes....
. However, in May 2000 this policy was reversed, and it was decided that arpa should be retained for this purpose, and int should be used solely by international organizations. In accordance with this new policy, arpa now officially stands for Address and Routing Parameter Area (a backronym
Backronym
A backronym or bacronym is a phrase constructed purposely, such that an acronym can be formed to a specific desired word. Backronyms may be invented with serious or humorous intent, or may be a type of false or folk etymology....
).
Beginning in March 2010 the arpa zone is signed (DNSSEC
DNSSEC
The Domain Name System Security Extensions is a suite of Internet Engineering Task Force specifications for securing certain kinds of information provided by the Domain Name System as used on Internet Protocol networks...
).
Second-level domains
The subdomains of arpa include- e164.arpa – ENUMEnumENUM or enum may refer to:* E.164 NUmber Mapping, a suite of protocols to unify the telephone system with the Internet* An enumerated type, a data type consisting of a set of named values...
lookup mapping telephone numbers into the DNS - in-addr.arpa – reverse DNS lookup for IPv4IPv4Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
addresses - ip6.arpa – reverse DNS lookup for IPv6IPv6Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
addresses - iris.arpa – For use in Cross Registry Information Service ProtocolCross Registry Information Service ProtocolThe Cross Registry Information Service Protocol, or CRISP, is a computer network communications protocol which has been in development by a working group at the Internet Engineering Task Force since 2004...
(CRISP) - uri.arpa – for dynamic discovery of Uniform Resource IdentifierUniform Resource IdentifierIn computing, a uniform resource identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network using specific protocols...
(URI) addressing schemes - urn.arpa – for dynamic discovery of Uniform Resource NameUniform Resource NameA uniform resource name is a uniform resource identifier that uses the urn scheme and does not imply availability of the identified resource. Both URNs and URLs are URIs, and a particular URI may be a name and a locator at the same time.The functional requirements for uniform resource names are...
(URN) addressing schemes