Final oversight, or authority, over the IANA functions has historically sat with the U.S. government. Initially, the task was carried out by Jon Postel, an employee of the University of Southern California, under contract to the U.S. Government's Defense Advanced Research Projects Agency (DARPA). In the late 1990s, the contracting party shifted from DARPA (an agency of the Department of Defense) to the NTIA (an agency of the Department of Commerce), while the role of contractor shifted from USC to the newly formed ICANN. Since 2000, the IANA functions contract has been held between NTIA and ICANN.
From as early as the so-called DNS White Paper issued by the NTIA in 1998, there was a clear intention on the part of the U.S. government to transition out of its role in coordination of the DNS.
Transitioning NTIA out of its role marks the final phase of the privatization of the DNS as outlined by the U.S. Government in 1997.
NTIA statement, March 2014
The specific, practical role of NTIA in stewardship of the IANA functions differs somewhat depending on the specific registry in question. For instance, approval of a change to the DNS root zone file requires an NTIA employee to verify that ICANN has followed the documented policy. No such sign-off is required for the IANA operator to make an Internet number resource allocation to an RIR, in line with existing policy.
Changes to the policies that govern how the IANA operator manages the global pool of Internet number resources (IP address and Autonomous System Numbers), Internet protocol parameters and the DNS root zone are developed through global, bottom-up processes.
A significant aspect of NTIA stewardship of the IANA function lies in the NTIA's role as the contracting party. In this role, the NTIA has the power to dictate the terms of the IANA functions contract and determine who will be contracted to carry out that role.