AWS to start charging for IPv4 usage, but critical services don't support IPv6

There is no "just" in this.

Copy-pasting from my other comment:

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IPv4 data structures have four bytes/octets (4B) for addresses. So how do you fit 8B of addresses in 4B structures? You don't. So you have to update every network element—host (desktop, laptop, mobile, embedded), router, switch, firewall—to have a new data structure (and maybe new function/system calls, as the old ones assume the old structures). So all devices have to have updated network stacks, including long-lived ones that sometimes are not touched for a decade+.

And not just pure networking code: anything that touches (e.g.) DNS as well, as A records are 4B-only as well, so you need a new record type and deploy new DNS server and resolver code everywhere.

But of course if you have a 4B-only network elements/devices, they cannot talk to 8B-only devices/services, so you have to create translation mechanisms because some devices may not yet have the update 8B-capable network stack. And sometimes an 8B network is an island in a sea of 4B, so you have to have tunneling. Of course some may have both 4B and 8B, and want to talk to something has also has 4B and 8B, so now you have to have code for source/destination selection.

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So "just" expanding IPv4 to IPv4+ ends up being the exact same amount of work as ended up with IPv6.

Only only thing you could say with "just" more addresses is keeping ARP and the like (instead of DAD, etc).

> Complete backwards compatibility

> If it's 8 bytes then it's a full address

Existing IPv4 devices wouldn't be able tell that it's 8 bytes, and wouldn't be able to make heads or tails of such a packet. At best, they discard the packet, at worse, they misinterpret it. It's not backwards compatible.

You can attempt to construe the bits however you like, but you're going to butt up against the pigeon-hole principle here. Any solution that works is going to be materially the same as IPv6.

CGNAT on IPv4 is not gonna save you from the Big Brother. IPv6 has many issues, but it is disingenuous to say the least that "it's a distraction from the big problems." The big problems you're talking about are completely unrelated to your IP packet version, and are not to be fought easily on this battlefield.