Internet Assigned Numbers Authority
As the Internet evolved, there was a need for a centralized organization which would fulfill the followings tasks/needs:
- To take responsibility for managing parameters
- To make sure that everyone uses the same protocols and parameters
- To coordinate the assignment of identifiers
- To ensure that the creation and allocation of addresses and domain names is done accurately, based on principles which are acceptable for everyone.
The organization which was responsible for these tasks/needs is IANA. Due to the Internet growth during the 1990's there was also the need for an organization that would take responsibility over the central registration of domain names and addresses. This is how ICANN (Internet Corporation for Assigned Names and Numbers) was created. 
ICANN is responsible for the centralization of registration tasks related to IP addresses, DNS assignment and protocol parameters management, but ICANN does not replace IANA. There are many differences between ICANN and IANA, especially regarding their attributions, objectives and responsibilities.
IANA vs ICANN
- IANA is the institution which runs TLDs (Top-Level Domains) and deals with the assignment of IP addresses and ranges, ports, and other related attributes.
- Besides managing the DNS root zone, IANA also manages the .int registry, and the .arpa zone;
- Regarding number resources, IANA is entitled to coordinate the global IP respectively AS number space, allocating these to RIRs (Regional Internet Registries);
- IANA represents the main repository for number registries and protocol names. 
In order to enable and better manage the allocation of Internationalized Domain Names (IDNs), IANA developed "IDN tables" which supply information related to admitted characters in different languages and other TLD related information. 
IANA is responsible for the delegation of IP Addresses to RIRs. In their turn, each RIR (Regional Internet Registry) is responsible for the allocation of IP addresses depending on the zone/area they are managing. In the same way, when a RIR requests for more IP Addresses for allocation, IANA evaluates the request and is able to make an additional allocation for RIR. 
Originally, the IANA functions is managed by the Information Sciences Institute (ISI) at the University of Southern California (USC) through the leadership of Dr. Jon Postel under a contract with the Defense Advance Research Project Agency (DARPA).
In 1997, the United States government under Pres. Bill Clinton's administration approved the transition of the technical management of the Domain Name System (DNS) including the IANA functions to a private sector. On January 30, 1998, the DOC released the Green Paper recommending the establishment of a new private, non-profit organization to take over the management of the DNS. The global internet stakeholders shared their comments and recommendations regarding the Green Paper and were compiled and studied by the NTIA. On June 1998, NTIA published the White Paper, which contains the policy statement of the U.S. government regarding the transition process for the technical management of the DNS to a new corporation that will be created based on the principles stability, competition, private bottom-up coordination and representation.
On November 25, 1998, the Department of Commerce formally recognized ICANN as the new organization responsible in administering the DNS through a Memorandum of Understanding signed by both parties.
The Department of Commerce (DOC) awarded a contract to ICANN to manage the IANA functions on February 9, 2000. The agreement was renewed several times in 2001, 2003,  and 2006 . The contract in 2006 was modified several times. The latest modification extended ICANN's contract for another 6 months until September 30, 2012.
DOC Notice of Inquiry on IANA Functions
On February 25, 2011, the DOC through NTIA issued a Notice of Inquiry (NOI) to review the IANA functions contract. ICANN's IANA functions contract expires on September 11, 2011. The internet community was encouraged to provide their feedback to the different questions posted by NTIA that aims help improve the operations of the IANA functions.The NOI is the first comprehensive review conducted by the DOC since ICANN took over the responsibilities of the IANA functions in 2000. The deadline for comments was scheduled on March 31, 2011. 
ICANN acknowledged the importance of a comprehensive review on the IANA Functions contract. ICANN suggested to change the conditions of the procurement contract between the U.S. government and internet governing body into a Cooperative Agreement. In addition, ICANN also recommended the include the principles of accountability and transparency in the next framework of the agreement and to restrict the scope of the IANA functions. ICANN will continue to perform the existing IANA function by entering separate agreements with the Internet Architecture Board (IAB) and the Internet Engineering Task Force (IETF) to perform the port and protocol parameter registry functions and the management of .arpa top level domain name (TLD).
On June 14, 2011, DOC issued a further NOI to solicit public comments regarding its draft Statement of Work (SOW), which consists the summary of comments submitted by the public to the first NOI, the response of the NTIA and the detailed work requirements for the IANA Functions.
RFP for New IANA Functions Contract
Following the NOI, the DOC published a Request for Proposal (RFP) for the new IANA Functions contract. Interested entities were encouraged to submit their proposals until December 12, 2011.
- IANA creations
- IANA attributions
- IANA Objectives
- IANA domains
- IANA IP Addresses
- Improvement of Technical Management of Internet Names and Addresses; Proposed Rule
- Statement of Policy on the Management of Internet Names and Addresses
- Second Status Report Under ICANN/US Government Memorandum of Understanding
- IANA Contract, February 9, 2000
- IANA Contract 2001
- IANA Contract 2003
- IANA Contract 2006
- Modification 10-Extension of IANA Contract
- DOC Notice of Inquiry
- A full guide to the new IANA contract
- ICANN Response to the DOC Notice of Inquiry
- Further Notice of Inquiry
- IANA RFP-Solicitation Number: SA1301-12-RP-IANA