If you wanted to connect the network for a new organization to the Internet you would need to contact an Internet Service Provider and make a connection. Your ISP would give you a range of IP addresses (i.e., one or more network numbers) that you could allocate to the computers attached to your network. The ISP assigns you network numbers by giving you a portion of the network numbers they received from a higher-level Internet Service Provider.
At the top level of IP address allocations are five Regional Internet Registries (RIRs). Each of the five registries allocates IP addresses for a major geographic area. Between the five registries, every location in the world can be allocated a network number. The five registries are North America (ARIN), South and Central America (LACNIC), Europe (RIPE NCC), Asia-Pacific (APNIC) and Africa (AFRNIC).
When the classic IPv4 addresses like “212.78.1.25” were invented, only a few thousand computers were connected to the Internet. We never imagined then that someday we would have a billion computers on the Internet. But today with the expansion of the Internet and the “Internet of things” where smart cars, refrigerators, thermostats, and even lights will need IP addresses, we need to connect far more than a billion computers to the Internet. To make it possible to connect all these new computers to the Internet, engineers have designed a new generation of the Internet Protocol called “IPv6”. The 128-bit IPv6 addresses are much longer than the 32-bit IPv4 addresses.4.8.
The Regional Internet Registries (RIRs) are leading the transition from IPv4 to IPv6. The transition from IPv4 to IPv6 will take many years. During that time, both IPv4 and IPv6 must work seamlessly together.