The Internet Assigned Numbers Authority (IANA) is responsible for maintaining a collection of registries that are critical in ensuring global coordination of the DNS root zone, IP addressing, and other Internet protocol resources. Since 1997, this role has been performed by ICANN, under a contract awarded by the National Telecommunications and Information Administration (NTIA), an agency in the U.S. Department of Commerce.
The IANA registries fall into three categories, each of which relate to a specific function in the Internet infrastructure:
The IANA includes the global registry for IPv4 and IPv6 addresses and Autonomous System Numbers (ASNs). These lists contain entries for all the IP address ranges and ASN blocks that are allocated for use on the Internet, as well as the Regional Internet Registry (RIR) to whom responsibility for these resources has been delegated. For instance, the entry for 18.104.22.168/8 points to the RIPE NCC as the responsible registry.
The IANA will make changes to the global IP address registries (such as allocating a block of IP address space to an RIR) according to policies developed and agreed on by the global community.
The Domain Name System (DNS) is a hierarchical distributed database that links domain names such as www.ripe.net to an IP address, which is then used to send data between computers. This can be compared to a phone book.
IANA maintains the top level of this hierarchy, the DNS root zone, which contains pointers to where information about second level domains, such as .com, .net and .nl can be found.
In order to make sure computers understand each other when communicating, certain numbers used in networking protocols need to have a globally unique meaning. These protocol parameters are defined as part of the technical protocol standards produced by the IETF. The IANA maintains and publishes these registries, which can then be used by software makers to ensure stable and predictable communications.