Internet Assigned Numbers Authority (IANA) is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Internet Protocol-related symbols and numbers. IANA is a department operated by the Internet Corporation for Assigned Names and Numbers, also known as ICANN.
Prior to the establishment of ICANN for this purpose, IANA was administered primarily by Jon Postel at the Information Sciences Institute (ISI) of the University of Southern California (USC), under a contract USC/ISI had with the United States Department of Defense, until ICANN was created to assume the responsibility under a United States Department of Commerce contract.
In the case of the two major Internet namespaces, namely IP addresses and domain names, extra administrative policy and delegation to subordinate administrations is required because of the multi-layered distributed use of these resources.
IANA delegates allocations of IP address blocks to Regional Internet Registries (RIRs). Each RIR allocates addresses for a different area of the world. Collectively the RIRs have created the Number Resource Organization formed as a body to represent their collective interests and ensure that policy statements are coordinated globally.
The RIRs divide their allocated address pools into smaller blocks and delegate them in their respective operating regions to Internet service providers and other organizations. Since the introduction of the CIDR system, IANA typically allocates address space in the size of /8 prefix blocks for IPv4 and /12 prefix blocks from the 2000::/3 IPv6 block to requesting regional registries as needed.
IANA administers the data in the root nameservers, which form the top of the hierarchical DNS tree. This task involves liaising with top-level domain operators, the root nameserver operators, and ICANN's policy making apparatus.
ICANN also operates the .int registry for international treaty organizations, the .arpa zone for Internet infrastructure purposes, including reverse DNS service, and other critical zones such as root-servers.
IANA administers many parameters of IETF protocols. Examples include the names of Uniform Resource Identifier (URI) schemes and character encodings recommended for use on the Internet. This task is undertaken under the oversight of the Internet Architecture Board, and the agreement governing the work is published in RFC 2860.
After the Astrolabe, Inc. v. Olson et al. lawsuit and the tz database's (or Timezone database, sometimes also referred to as the Olson database after its creator) eventual shutdown, IANA resumed operation of the database on October 16, 2011. The tz database holds the timezone differences and rules for the various regions of the world and allows this information to be mirrored and used by computers and other electronic devices to keep accurate track of timezones through the Internet.