John Levine wrote on 18/11/2021 03:03:
The amount of work to change every computer in the world running TCP/IP and every IP application to treat 240/4 as unicast (or to treat some of 127/8) is not significantly less than the work to get them to support IPv6. So it would roughly double the work, for a 2% increase in the address space, or for 127/8 less than 1%. The code for IPv6 is already written, after all.
Also, while the world has run out of free IPv4 address space, there is plenty of IPv4 if you are willing to pay for it. A 2% increase in v4 addresses would not change that.
putting more numbers on the table, the pre-exhaustion burn rate of unallocated ipv4 address space was around 13 x /8 a year, i.e. a /8 every four weeks. The ask is to update every ip stack in the world (including validation, equipment retirement, reconfiguration, etc) and the gain is 4 weeks of extra ip address space in terms of estimated consumption. Nick