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Wouldn't this proposal not require isps to do anything? They already assign every user a unique ipv4 address. Then, with this proposal, if I want to have a bunch of computers behind that single ipv4 ip, I could do it without relying on NAT tricks

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> 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.

ISPs that want to split it up could do so, while other ISPs just stick to v4. Provided the hosts at least understand v4x.

If that happens then the user can only communicate with hosts supporting IPv4x and you're back to the IPv6 issue

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.

There aren’t enough IPv4 addresses to give everyone one. That is why ISPs use CGNAT to hide multiple customers behind one IP address.

Something that just uses IPv4 won’t work without making the extra layer visible. That may not have been apparent then but it is now.

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