.arpa
| Introduced | January 1, 1985 |
|---|---|
| TLD type | Infrastructure domain |
| Status | Active |
| Registry | IANA |
| Sponsor | Internet Architecture Board |
| Intended use | Address and Routing Parameter Area: Internet infrastructure such as reverse IP lookup. |
| Registration restrictions | No domain registrations possible, new subdomains rarely added |
| Structure | Second-level domains provide special name spaces for database functions |
| Documents | RFC 3172 |
| Dispute policies | None |
| Website | IANA .arpa info |
| DNSSEC | yes |
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 was originally the acronym for the Advanced Research Projects Agency (ARPA), the funding organization in the United States that developed one of the precursors of the Internet (ARPANET), 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.
As of 2015, IANA distinguishes the following groups of top-level domains:
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.
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