Comment by boredatoms

It was never going to be a clean cut, which is why we didn't design it for a clean cut and instead developed a bunch of approaches to transitioning to it that deal with the real-world problems of the transition.

What more do you want from it?

What could they have possibly done differently to make you happy with it?

> people who either worked for the likes of Google who were aching for a globally unique identifier per device

v6 doesn't give you globally unique device identifiers. Devices get IPs from the network in v6, just like they do in v4. You're either thinking of MAC addresses or perhaps things like HIP (https://datatracker.ietf.org/doc/html/rfc7401). I guess there is Mobile IPv6 which allows you to take your address to another network, but then there's also privacy extensions which prevent your machine from using the same IP for very long, so it's still not a unique identifier for your device.

> Yeah, that is the whole point. It was never going to be a clean cut.

As predicted:

      We believe that it is not possible to have a "flag-day" form of
      transition in which all hosts and routers must change over at
      once. The size, complexity, and distributed administration of the
      Internet make such a cutover impossible.

      Rather, IPng will need to co-exist with IPv4 for some period of
      time.  There are a number of ways to achieve this co-existence
      such as requiring hosts to support two stacks, converting between
      protocols, or using backward compatible extensions to IPv4.  Each
      scheme has its strengths and weaknesses, which have to be weighed.

      Furthermore, we note that, in all probability, there will be IPv4
      hosts on the Internet effectively forever.  IPng must provide
      mechanisms to allow these hosts to communicate, even after IPng
      has become the dominant network layer protocol in the Internet.

* https://datatracker.ietf.org/doc/html/rfc1726#section-5.5

Creating an IPng was always going to be complicated:

      So it's a matter of mathematical and physical fact that to expand
      the address size, you must change the protocol, and that means 
      [three] things immediately:

            You have to change the version number.

            You have to add new code to handle the new version.

      […]

            You need a coexistence technique so that updated systems, 
            with the new protocol, can connect to old systems that know 
            nothing of the new protocol.

      Two minutes of thought show that this third requirement has only 
      two solutions:

            (3A) Dual stack, in which the new machines speak both 
                 the old (IPv4) and new (IPng) protocol.

            (3B) Translation, in which something translates addresses
                 between the old and new protocols.

* https://github.com/becarpenter/misc/blob/main/why6why.md

* https://datatracker.ietf.org/doc/html/rfc1671

> The issue isn't that it wasn't planned properly, the issue is that the real world wasn't taken into consideration by people who either worked for the likes of Google who were aching for a globally unique identifier per device or just delusional about how much we can change in real world.

All this complaining and not so much as a single hint or even belief that there's a better solution.

I suppose we could read into the complaint some kind of faith that one does exist, but since nobody has found it yet, the faith is a little uncompelling so far.