My thanks to Mr. Robert Bender for this resource
Excerpt:
The Internet will soon be sailing in very rough seas, as it’s about to run out of addresses, needing to be gutted and reconfigured for continued growth in the second half of the 2010s and beyond. Originally, the idea was that this upgrade would happen quietly in the background, but over the past few years, it has become clear that the change from the current Internet Protocol version 4, which is quickly running out of addresses, to the new version 6 will be quite a messy affair.
Also see:
IP Address Block Size Equivalents in Classful Addressing, IPv4, and IPv6 — from American Registry for Internet Numbers (ARIN)