All public IP addresses are ostensibly managed by Internet Corporation for Assigned Names and Numbers (ICANN). However, it is the Internet Assigned Numbers Authority (IANA) that handles the day-to-day management of IP addresses on behalf of ICANN. IANA allocates huge chunks of IP address space to Regional Internet Registrars (RIR) who either allocate or assign IP addresses to ISP's or end users, respectively. The Regional Internet Registrar for North and South America and the carribean is ARIN, the American Registry for Internet Numbers.
Originally, IP addresses were assigned by Jon Postel (yes, just one human being) until such time as the workload and number of requests became too large for one individual to handle and so IANA was created. ICANN formed itself and appointed itself the managing entity of everything Internet shortly after Jon Postel's death in 1998 (an unprecedented power grab in the history of the Internet--yet nobody complained).
IANA was formed to coordinate the global management of the DNS root, global IP addressing, assignment of BGP Autonomous System numbers worldwide as well as Protocol and port numbers.
The Regional Internet Registries
The actual assignment or of IP addresses is performed by Regional Internet Registries (RIR's):
- ARIN - North and South America
- RIPE NCC - Europe, Middle East and Central Asia
- APNIC - Asian Pacific
- LACNIC - Latin America
- AfriNIC - African Continent
The Regional Internet Registries (RIR) are responsible for the following:
- Managing all IP address assignments and allocations (both IPv4 and IPv6) in their region
- Managing all Autnonomous System Number assignments.
- Maintaining public directories, such as:
- The WHOIS directory/registry containing registration transaction information
- Routing information (though this function is no longer maintained)
- Root Reverse DNS resolution
You can obtain public IP addresses without buying them from an ISP, but you only need public IP addresses if you have Internet access and you need a public address to support a website, e-mail or DNS.
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