Which of the following is NOT a Regional Internet Registry?

The Internet Assigned Numbers Authority (IANA) is not categorized as a Regional Internet Registry (RIR). IANA is responsible for overseeing global IP address allocation, protocol parameter assignments, and the management of the DNS root zone, but it does not function as an RIR that allocates IP addresses to specific geographic regions.

In contrast, organizations like the American Registry for Internet Numbers (ARIN), the Réseaux IP Européens Network Coordination Centre (RIPE NCC), and African Network Information Centre (AfriNIC) are RIRs that manage and distribute IP address resources within their respective regions. Each of these RIRs serves particular geographic areas, ensuring that local Internet Service Providers (ISPs) and organizations can obtain the required IP addresses for their networks.

Thus, the correct identification of IANA as not being an RIR helps clarify the distinct roles each of these organizations plays in Internet governance and resource management.