The Internet Assigned Numbers Authority (IANA) is the entity that oversees global IP address allocation, DNS root zone management, media types, and other Internet protocol assignments. It is operated by ICANN.
Prior to the establishment of ICANN for this purpose, IANA was administered primarily by Jon Postel at the Information Sciences Institute at the University of Southern California, under a contract USC/ISI had with the United States Department of Defense, until ICANN was made to assume the responsibility under a United States Department of Commerce contract.
IANA is broadly responsible for the allocation of globally-unique names and numbers that are used in Internet protocols that are published as RFC documents. It maintains a close liaison with the IETF and RFC Editor in fulfilling this function.
In the case of relatively high-profile subsets of protocol numbers - namely IP addresses and domain names, extra policy and handling is required and the allocation process is handled in more specific methods. This is to cope with the multi-layered administration of these resources.
IANA delegates the allocation of IPv4 addresses to RIRs in large blocks (typically in the size of "/8", or 224 addresses, or more at a time), and the RIRs then re-allocate smaller blocks in the regions to ISPs and other organizations.
There is also a process for the delegation and allocation of IPv6 addresses, but there is currently little delegation pressure on blocks of IPv6 addresses, as supply vastly exceeds demand.
On January 28, 2003 the DOC, via the Acquisition and Grants Office of the National Oceanic and Atmospheric Administration, issued a notice of intent to grant ICANN the IANA contract for three more years. It invited alternative offerors to submit in writing a detailed response on how they could meet the requirements themselves. Such responses were to be received no later than 10 days following publication of the invitation and the decision on whether to open the "tender" to competition was to remain solely within the discretion of the government.
The relationship between ICANN and the ccTLDs and RIRs can best be described as highly political, and there have been a number of proposals to decouple the IANA function from ICANN completely. However, it is widely believed that it would be impractical to change the current control structure without risking fracturing the Internet.
The earliest reference to a registry function is probably RFC 322, published on March 26, 1972, which had Vint Cerf and Jon Postel establishing a "socket registry" - this registry was published in the RFC series as RFC 433 in December 1972.
The first reference to the name "IANA" in the RFC series is in RFC 1060, published in 1990, but the function, and the term, was well established long before that; RFC 1174 says that "Throughout its entire history, the Internet system has employed a central Internet Assigned Numbers Authority (IANA)...", and RFC 1060 lists a long series of earlier editions of itself, starting with RFC 349.
Jon Postel managed the IANA function from its inception until his death in October 1998. After his death, Joyce Reynolds, who had worked with him on IANA for many years, managed the transition of the IANA function to ICANN.
The reason why Postel had the authority to perform the IANA function was that he had always done it in his position at the Information Sciences Institute, under its DoD contract, and did it well.
Starting in 1988, IANA was funded by the U.S. government under a contract between the Defense Advanced Research Projects Agency and Information Sciences Institute (ISI). This contract expired in April 1997, but was extended to preserve IANA's function.
On December 24, 1998, USC entered into a transition agreement with the Internet Corporation for Assigned Names and Numbers ICANN, transferring the IANA function to ICANN, effective January 1, 1999, thus making IANA an operating unit of ICANN.
On February 8, 2000, the DoC entered into an agreement with ICANN to perform the IANA functions.
In November 2003, Doug Barton was appointed IANA manager.
In 2005, David Conrad was appointed as IANA manager.