Jon Postel is also responsible for the Internet Assigned Numbers Authority (IANA) which back in the day basically managed the Internet by keeping a central repository of the addresses, names, and protocol parameters on the Internet since its start. This same organization later adopted Jon’s suggestion to replace the number addresses with the domain names: RFC-1591.
Today, IANA is huge. They maintain a high-level registry of IP addresses and there are regional registries covering the globe. IANA works with the Regional Internet Registries (RIRs) to distribute the large blocks of IP addresses among the RIRs. There are currently 4 RIRs, distributed around the world: APNIC (Asia/Pacific Region), ARIN (North America and Sub-Sahara Africa), LACNIC (Latin America and some Caribbean Islands), and RIPE NCC (Europe, the Middle East, Central Asia, and African countries located north of the equator). A fifth regional registry is in formation for Africa (AfriNIC). The RIRs are the organizations that actually allocate IP addresses to ISPs. These allocations are in smaller blocks of addresses.