On 24 October 2003, the four existing RIRs – APNIC, ARIN, LACNIC, and RIPE NCC – entered into a Memorandum of Understanding (MoU) with ICANN to form the Number Resource Organization (NRO).

The NRO is a coordinating body for the five Regional Internet Registries (RIRs) that manage the distribution of Internet number resources including IP addresses and Autonomous System Numbers. Each RIR consists of the Internet community in its region.

Following its incorporation in April 2005, AFRINIC signed a MoU with the NRO.

The NRO also acts as the ICANN Address Supporting Organization (ASO), formed to review and develop recommendations on IP address policy and to advise the ICANN Board. An elected body called the NRO Number Council (NRO NC) serves as the ASO Address Council (ASO AC), overseeing recommendations on IP address policy, including the management of policy development activities, and appoint members to the ICANN Board of Directors.

Each of the RIRs appoints three members of the ASO Address Council. Two members are selected by the regional policy forum of each of the RIRs and one member is appointed from the Executive Board of each RIR.

You can read more on the ASO AC/NRO NC here