ⓘ .arpa


ⓘ .arpa

The domain name arpa is a top-level domain in the Domain Name System of the Internet used exclusively for technical infrastructure purposes. The name was originally a reference to the precursor of the Internet, ARPANET, from which the domain was intended to facilitate the transition to DNS, but it now stands for Address and Routing Parameter Area.

arpa also contains the domains for reverse domain name resolution in-addr.arpa and ip6.arpa for IPv4 and IPv6, respectively.


1. History

The arpa top-level domain was the first domain installed in the Domain Name System 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 one of the predecessors 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 i.e., a period. 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 addresses. For example, the mapping of the IP address to a host name is obtained by issuing a DNS query for a pointer record of the domain name

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.

Since March 2010, the arpa zone is signed with DNSSEC.

In May 2018.home.arpa was ratified as a special-use domain and the sanctioned TLD for residential private networks.