> Wouldn't this proposal not require isps to do anything? They already assign every user a unique ipv4 address.
The reason there's an IPv4 address shortage is because ISPs assign every user a unique IPv4 address. In this alternative timeline, ISPs would have to give users less-than-an-IPv4 address, which probably means a single IPv4x address if we're being realistic and assuming that ISPs are taking the path of least resistance.
As long as IPv4x support was just something you got via software update rather than a whole separate configuration you had to set up, the vast majority of servers probably would have supported IPv4x by the time addresses got scarce.
However, if it did become a problem, it might be solvable with something like CGNAT.
CGNAT would also be easier on routers too, since currently they need to maintain a table of their port being used to the destination ip and port. Whereas with ipv4x, the routing information can be determined from the packet itself and no extra memory would be required
That's only true when forwarding IPv4x -> IPv4. When you're going the reverse direction and you need to forward IPv4 -> IPv4x, well, still need a table then.
The reason there's an IPv4 address shortage is because ISPs assign every user a unique IPv4 address. In this alternative timeline, ISPs would have to give users less-than-an-IPv4 address, which probably means a single IPv4x address if we're being realistic and assuming that ISPs are taking the path of least resistance.