[ghshephard]

IANA and the RIRs are stepping away from their requirement that everyone route through their ISP's parent space. They quickly discovered there are a lot of reasons why Provider Independent Address Space (PIAS) is critical to any real business, and that nobody is going to re-number when they change ISPs (not to mention the hassle of having to deal with multi-site environments). The entire concept was a pipe dream.

If they hadn't yielded on PIAS then every enterprise network engineer out there was just going to deploy in RFC 4193 ULA space, say screw you to the IETF and implement RFC 6296 - NPTv6 on their perimeter.

Net-Net - Once IPv6 starts to get traction, we're going to have routing tables of roughly the same size, but they'll just consist of /48s instead of /20s.

[tjgq]

Deploying RFC 4193 at least would not pollute the global routing table with lots of short prefixes. Those enterprise networks would pay for that flexibility themselves instead of forcing the cost onto the whole Internet.

[ghshephard]

Routers have gotten much, much faster, and memory has gotten much, much bigger. And a lot of the Longest Prefix Match stuff is highly optimized/fast switched anyways now.

[tjgq]

Hence my inital premise: if memory hadn't gotten so cheap, we would have transitioned into IPv6 already. For all the good Moore's Law brought us, it is also the reason why we seem to be stuck in this NAT world with no end in sight.

[ghshephard]

The original belief with IPv6 is that End Users would route through their ISPs address space, and the IPv6 made renumbering so easy, that it would be simple for end-users to change providers and renumber.

This turns out not to be the case.

IPv6 will not reduce the size of the routing tables. Anybody with prefixes, and PIAS right now, will likewise get a /48 of IPv6 space and start advertising it into BGP.

If anything the more easily available space may result in bigger routing tables as a result. (Not everyone was able to get a /20 - particularly outside of ARIN space. For example - IPv4 addresses come very dear in places like Dubai.)

And NAT doesn't go away with IPv6. That was another belief that did not survive its first encounter with reality. It's simply called "Network Prefix Translation" now (NAT by another name)

[tjgq]

> And NAT doesn't go away with IPv6. That was another belief that did not survive its first encounter with reality.

If it doesn't go away, it will be only because of ISP greed (i.e., charging customers for a larger number of publicly routable addresses). Otherwise, there simply is no reason not to give every customer a /56 or even a /48, given that routers won't be able to route prefixes longer than that anyway.

Fortunately, most ISPs offering native IPv6 so far have turned out not to be that greedy.

[ghshephard]

It has nothing to do with ISP greed. There is no shortage of IPv6 addresses, and, ISPs have every motivation to encourage their customers to use their IPv6 space.

The reason NAT doesn't go away is that customers don't want to use their ISPs IPv6 space, they want their own provider independent space.

The easiest way to do that, is to address all your devices from RFC 4193 ULA space, and then, on your perimeter, do RFC 6296 Network Prefix Translation to the ISPs IPv6 space.

Then, when you change ISPs, you simply make a single change on your perimeter rather than having to renumber hundreds of internal devices, DNS, configurations, etc...