.arpa是互联网域名系统上一個专门用于互联网基础设施配置的頂級域。其名称最初是缩写自高等研究計劃署(Advanced Research Projects Agency,ARPA),也就是现在互联网的雏形网络ARPANET的主管部门。现在其标准名称对应为“地址路由参数域(Address and Routing Parameter Area)”。直到2015年,它是IANA顶级域分类中的一个分类,基础设施顶级域(infrastructure top-level domain)内的唯一顶级域。[1]
原计划,一个新的顶级域“.int”被设立用来替代该域名的数据库结构机制,但2000年5月原计划被推翻了,本顶级域的功能仍被保留,新的顶级域被用于国际组织的域名分类。[7]而这次计划变更后,本顶级域被赋予正式的官方名称,名称被定为“地址路由参数域(Address and Routing Parameter Area)”。[8]
^O., Bruen, Garth. WHOIS running the Internet : protocol, policy, and privacy. WHOIS Running the Internet: Protocol, Policy, and Privacy. Hoboken, New Jersey. : 138 [2017-11-30]. ISBN 9781118985779. OCLC 912140475. (原始内容于2017-12-01).
^RFC 1035, Mockapetris, Paul. IN-ADDR.ARPA domain. Domain Names - Implementation and Specification. Internet Engineering Task Force. November 1987: pp. 22 – 23. sec. 3.5 [2009-10-28]. RFC 1035.
^IAB Statement on Infrastructure Domain and Subdomains. [2009-05-08]. (原始内容存档于2009-05-11).
^RFC 3172, Huston, Geoff. Management Guidelines & Operational Requirements for the Address and Routing Parameter Area Domain ("arpa"). Internet Engineering Task Force. September 2001: p. 7 [2009-10-28]. BCP 52. RFC 3172. Further, as indicated by DARPA, the arpa TLD string should be given a different expansion such as "Address and Routing Parameter Area" to avoid any implication that DARPA has operational responsibility for the domain.