I wouldn't say "failure". There are many, many IPv6 client devices out there, mostly on mobile networks. And it works great and they do well and the tools all support it very well.

But IPv4 will never, ever die. The rise of NAT as a pervasive security paradigm[1] basically neuters the one true advantage IPv6 brought to the table by hiding every client environment behind a single address, and the rise of "cloud everything" means that no one cares enough about reaching peer devices anyway. Just this morning my son asked me to share a playlist, so of course I just send him a link to a YouTube Music URL. Want to work on a spreadsheet for family finances with your spouse in the next room? It lives in a datacenter in The Dalles.

[1] And yes, we absolutely rely as a collective society on all our local devices being hidden. Yes, I understand how it works, and how firewalls could do this with globally writable addresses too, yada yada. But in practice NAT is best. It just is.

> I wouldn't say "failure". There are many, many IPv6 client devices out there, mostly on mobile networks.

Honestly it's a huge success due to this fact alone.

IPv6 is failure only if you measure success by replacing IPv4 or if you called "time" on it before the big mobile providers rolled it out. The fact that all mobile phones support it and many mobile networks exclusively deploy it tells you what you really need to know.

IPv6 is a backbone of the modern Internet for clients, even if your servers don't have to care about it due to nat64.