Why IPv6?

The main reason is that there simply aren't enough IPv4 addresses available!

There are 4,294,967,296 (2³²) IPv4 addresses available.

When IPv4 was being designed 30 years ago, the creators had no idea the Internet would be as large as it is today.

VLSM, private IPv4 addresses, and NAT have been used to conserve the use of IPv4 address space.

Those are short-term solutions.

The long-term solution is IPv6.

IPv4 address assignments are controlled by IANA.

IANA distributes IPv4 address space to various RIRs (Regional Internet Registries), which then assign them to companies that need them.

On 24 September 2015 ARIN declared exhaustion of the ARIN IPv4 addresses pool.

On 21 August 2020, LACNIC announced that it had made its final IPv4 allocation.