Based on the way IPv6 is currently allocated we only leverage about 56 bits of usable address space but IPv4 with NAT gives us a max of 96 bits of address space because it's a 5-tuple

> IPv4 with NAT gives us a max of 96 bits of address space

But then you need NAT piercing everywhere for even "basic use". How is not being able to connect to things "usable"?

By that same metric, you also get a bare minimum, naive count of of 144 bits of IPv6 address with 2 layers of link-local address + all ports.

144 is much larger that 96.

Even the naive 64 bits "just use one layer of link-local" is still larger that the entire current 32-bits of IPv4.

I think the point is that 96 is quite enough to not run out. Which is plausibly fair, if you can actually get that many bits (or close enough to actually cover everyone) and can deal with the ugliness of NAT. It's especially fair, I think, to argue that the reason that IPv6 adoption has been so slow is because IPv4+NAT is good enough for most people. Just because IPv6 is better doesn't mean that people will want it if the old option can be hacked up to keep working.

So is 56. That’s about 9 million addresses for every human on earth.

And, of course OP is wrong about 56 anyway, but so it goes

Oh, sure; arguing that IPv6 doesn't, in any way shape or form, have enough addresses would be extremely misguided. I was reading it as "IPv4 already has enough address space (if we include NAT) so we don't need to deal with v6".

FYI: After skimming the article, I'm downvoting because you conflated what the article calls "This 96-bit NAT address space is a highly theoretic ceiling, […]" became a plain unqualified "96 bits of address space" in your comment. Which you're then comparing with the "56 bits of usable address space" in IPv6.

Also, that sentence continues in the article with: "[…] but the pragmatic question is how much of this space can be exploited in a cost-effective manner such that the marginal cost of exploitation is lower than the cost of an IPv6 deployment."

Pretty much anything is lower than the cost of IPv6 deployment if you already have a large IPv4 deployment.

CGNAT routers aren't cheap. At some point you're spending more keeping your IPv4 running than it would take to replace it.

Except you can't really replace it. You need to keep BOTH for the good old internet to work.

You probably need some amount of CGNAT or equivalent (e.g. DS-Lite). But if you offload the vast majority of your traffic onto v6 (which is easier than it sounds, because most traffic is to a few big sites and most of them are v6-enabled) then you can reduce the number of connections you have to track by orders of magnitude, which saves you real money.

Yeah I remember seeing that in a talk about an ISP adding IPv6 support: https://youtu.be/75h4gm7t1oI . They say that 30% of traffic is IPv6, which means 30% less CGNAT hardware needed.

> If that's everything IPv6 has going for it it's no wonder its adoption is still so low

IPv6 has numerous things going for it. But it also has numerous downsides. I suspect that's why the adoption is so slow.