I don't think the original rollout of the v4 internet really counts as a migration project, because there was no "NetBEUI internet" or "AppleTalk internet" to migrate from in the first place. IPX/SPX/NetBEUI/AppleTalk/DECnet all either run on only a single L2 network, or were only used in small, local groups of networks. Nothing existed that linked every network on the planet together in a single shared address space. You can't migrate a global network from one protocol to another when the global network you're migrating from doesn't exist yet; that's a new deployment, not a migration.

As a result, network effects [in the economic sense of the term] worked in favor of deploying v4, but they work against deploying any replacement to v4.

You could argue that it required migrating local networks, and it did, but migrating from IPX/etc to IP is fundamentally simpler than migrating v4 to v6, because you only need to worry about your local network -- which you have full authoritative control over and can mandate a migration deadline for. You didn't need to worry about maintaining compatibility with the IPX Internet either, because there wasn't one.

Note that I'm drawing a distinction between a network and an internet. IPX/etc only did the former, IP does both. The level of challenge in migrating a network (even multiple of them) is very different to migrating an entire internet, due to the interconnectivity or lack thereof between the networks.

You're also talking about a time when there were three orders of magnitude fewer networked computers, and relatively little networked software except for the vendor software that came with the network stacks in the first place, which wasn't expected to be compatible with any other network protocol.

Moving from static networks and hosts files to DNS and DHCP, is all L4 stuff, and could be done without changing L3. Similarly with firewalls and NAT: there's no need to change L3 to implement those and their deployment is a local-network-only project.

You make a good point that the 90s had far more technological change -- it must have been interesting to live through. But it was technological change that was fundamentally easier to deploy because it only involved making local changes on each network, not changes on all networks. v6 doesn't have that luxury because v6 is replacing the IP address, which is the one thing that goes end-to-end through all of the networks.

So yeah, that's my argument for not agreeing that the original rollout of v4 was bigger or harder than v6, even though it involved more technological changes. It's not the technical difficulty but the sheer scale of the deployment -- v6 needs to deal with far, far more software, devices, networks and involved people than anything v4 had to deal with in the 90s -- and the strength of the network effects that worked in v4's favor but which are working against v6.

> Similarly, although it's not my area, it's an interesting line of questioning to ask "what is wrong with IPv6 that the world didn't move to it, and can we fix that?"

I don't think it's fair to say that the world didn't move to v6, because the world is moving to v6. It's gone from 50 million users to 2.3 billion users in the last 10 years. That's about the number of people that were using v4 at the start of those 10 years.

I'm not treating these questions as heresy, it's just that we keep seeing the same broken takes over and over and it gets very tiring. Things like "v6 would have been deployed in 5 years if they had just added some zeros to the beginning of v4 addresses", from somebody who doesn't have a clue how to make that work and who doesn't know enough to realize that it can't work. There are dozens of people like that just in the comments to this article alone. You can't expect posts like that to be taken seriously by anyone that knows what they're talking about.

> It's good but it only fixes 1 problem

It's interesting that you say this, because the person I replied to above said "I think it was protocol design hubris: we are fixing SO MUCH STUFF that people will flock to this irresistible shining trophy of protocol design."

Is it fixing too much stuff or too little stuff? You guys can't even agree on that!