[btilly]

I agree with that belief, and I've been saying it for over 20 years.

I base it on comparing how the IPv2 to IPv4 rollout went, versus the IPv4 to IPv6 rollout. The fact that it was incredibly obvious how to route IPv2 over IPv4 made it a no-brainer for the core Internet to be upgraded to IPv4.

By contrast it took over a decade for IPv6 folks to accept that IPv6 was never going to rule the world unless you can route IPv4 over it. Then we got DS-Lite. Which, because IPv6 wasn't designed to do that, adds a tremendous amount of complexity.

Will we eventually get to an IPv6 only future? We have to. There is no alternative. But the route is going to be far more painful than it would have been if backwards compatibility was part of the original design.

Of course the flip side is that some day we don't need IPv4 backwards compatibility. But that's still decades from now. How many on the original IPv6 will even still be alive to see it?

[Macha]

The IPv2 to IPv4 migration involved sysadmins at less than 50 institutions (primarily universities and research labs), updating things they considered to be a research project, that didn’t have specialised network hardware that knew anything about IP, and any networked software was primarily written either by the sysadmins themselves or people that one of them could walk down the corridor to the office of. Oh, and several months of downtime if someone was too busy to update right now was culturally acceptable. It’s not remotely the same environment as existed at the time of IPv6 being designed