less than half of all netizens use IPv6 today.

To understand why, know that IPv6 also suggested other, rather modest, changes to the way networks operate.

"IPv6 was an extremely conservative protocol that changed as little as possible," APNIC chief scientist Geoff Huston told The Register. "It was a classic case of mis-design by committee."

And that notional committee made one more critical choice: IPv6 was not backward-compatible with IPv4, meaning users had to choose one or the other – or decide to run both in parallel.

For many, the decision of which protocol to use was easy because IPv6 didn't add features that represented major improvements.

"One big surprise to me was how few features went into IPv6 in the end, aside from the massive expansion of address space," said Bruce Davie... //

Davie said many of the security, plug-and-play, and quality of service features that didn't make it into IPv6 were eventually implemented in IPv4, further reducing the incentive to adopt the new protocol. "Given the small amount of new functionality in v6, it's not so surprising that deployment has been a 30 year struggle," he said. //

While IPv6 didn't take off as expected, it's not fair to say it failed.

"IPv6 wasn't about turning IPv4 off, but about ensuring the internet could continue to grow without breaking," said John Curran, president and CEO of the American Registry for Internet Numbers (ARIN).

"In fact, IPv4's continued viability is largely because IPv6 absorbed that growth pressure elsewhere – particularly in mobile, broadband, and cloud environments," he added. "In that sense, IPv6 succeeded where it was needed most, and must be regarded as a success." //

APNIC's Huston, however, thinks that IPv6 has become less relevant to the wider internet.

"I would argue that we actually found a far better outcome along the way," he told The Register. "NATS forced us to think about network architectures in an entirely different way."

That new way is encapsulated in a new technology called Quick UDP Internet Connections (QUIC), that doesn't require client devices to always have access to a public IP address.

"We are proving to ourselves that clients don't need permanent assignment of IP address, which makes the client side of network far cheaper, more flexible, and scalable," he said.