[daurnimator]

I've heard that a lot of ISPs in Australia are stuck on IPv4 as their whole billing systems (written in early 2000s) use IPv4 addresses for everything. Including techniques like mapping an array of size 2^32 (entirely possible with virtual addresses) to keep counters for each user. It would be a complete rewrite of their billing systems to work with IPv6, and they no longer have many/any programmers on staff.

[Dagger2]

There's no particular reason to use the entire IP as the lookup key though; all customers will be numbered out of the ISP's single allocation and you don't need to keep track of the traffic of each individual host, just the overall traffic of each customer.

You'd end up needing a much smaller array for v6 -- small enough that you could fit it into the presumably-unused parts of those 2^32 arrays that correspond to the v4 class E space.

[jwhite]

Most residential customers don't have static IP addresses -- how does that work when a customer's IPv4 address changes?

[daurnimator]

I believe they take a snapshot (which can be as simple as fork(), hooray for COW memory) of the array every minute to see how much you've downloaded. The same IPv4 address isn't reused by another customer until a day has passed.

[M_Bakhtiari]

>Most residential customers don't have static IP addresses

Where is this? What do you have to back up this claim?

>how does that work when a customer's IPv4 address changes?

As far as I can tell, it wouldn't. But I don't see what your point is.

I'm not in Australia, but I've had the same IP for decades, even having gone through multiple routers, so it's probably tied to the DSLAM port I'm connected to, which makes sense for such a billing scheme. Also might be why I don't have IPv6 yet either.