[Dagger2]

That's not true. For connections initiated from the v4 network, you can deploy v6 on the network, use a proxy, or use 6to4, 6rd or Teredo. For connections initiated from v6, you can use NAT64. There are also various approaches to deploy one protocol over the other, like 6over4, DS-lite, 464xlat, MAP-T/E, 4rd or LW4over6.

Pretty much every interoperability method that can work with v4 is supported by v6. How is that an interoperability failure?

> Pretty shit transition plan if we've only managed to get 35% of devices on v6 in 25 years.

The plan is "start using v6, then stop using v4". What better plan do you suggest?

I'd call it more like 35% in 9 years, since Google's stats say that deployment was <1% in 2013. (The time before that was spent on updating protocols, implementing the updated protocols in software and hardware, and deploying the updates, all of which are necessary prerequisites before users can show up in those stats.)

That seems like pretty decent going, given the sheer scale of what needs to be done.

[commandersaki]

> That's not true. For connections initiated from the v4 network, you can deploy v6 on the network

Having a v6 address on a v4 network doesn't make it a v4 only network. The vast majority of networks are v4 only. If the designers cared enough about interoperability and migration they would've spent time working on a plan to have these v4 only networks talk to v6. The transition plan would be seamless since the inherent value of a v4 address and a v6 address would be the same. If you look at the ngtrans mailing list, they pretty much gave up on a transition plan in the end, and there's still a bunch of deployment guides, even "best practices", but there's still no transition plan except this "get on v6, get off v4" rubbish.

The only reason the numbers are so high is because of Mobile since the telecom carriers have full control of the IP stack on the handset.

[Dagger2]

Again, what plan do you suggest? v6 already does everything that can be done with v4, yet that's not good enough for you. What more could they have done?

It's not fair to blame them for not being able to do the impossible.

[commandersaki]

The other choices for IPng at least tried to have an actual transition plan that would involve IPv4-only networks connecting to IPng. In fact the IPng criteria requirements outlined there be a straightforward transition plan from IPv4 that was simple and realistic. Then they settled for IPv6 which had no transition plan and still doesn't have one that meets the criteria set forth in the IPng requirements -- to this day.

The selection committee and ngtrans are to blame for not ever coming up with a transition plan that included interoperability with IPv4 as a basic tenet. They've effectively made IPv6 a second class protocol and will probably end up being like this forever.

IPv6 is effectively a waste of time, and that's how it's seen by most enterprise and ISPs. I'm holding out hope for research in future Internet architectures that will hopefully not make the same mistake as IPng and instead come up with actual transition plans with their designs.

[Dagger2]

What were those other choices/what transition plan did they have?

v6 does have a transition plan, and as far as I can tell it's not really possible to do any better than it's already doing. v6 is as interoperable with v4 as is possible to be, given the design of v4.

Can you explain how it could have been better? What transition plan would meet your requirements?