I don't like to admit this, but at this point honestly I think ipv6 is largely a failure, and I say this as someone that wrote a blog post for APNIC on how to turn on ipv6.

I'll get endless pushback for this, but the reality is that adoption isn't at 100%, it very closely needs to be, and there are still entire ISPs that only assign ipv4, to say nothing of routers people are buying and installing that don't have ipv6 enabled out of the box.

A much better solution here would have been an incredibly conservative "written on a napkin" change to ipv4 to expand the number of available address space. It still would have been difficult to adopt, but it would have the benefit of being a simple change to a system everyone already understands and on top of a stack that largely already exists.

I'm not proposing to abandon ipv6, but at this point I'm really not sure how we proceed here. The status quo is maintaining two separate competing protocols forever, which was not the ultimate intention.

> A much better solution here would have been an incredibly conservative change to ipv4 to expand the number of available address space

"And what do you base this belief on?

Fact is you'd run into exactly the same problems as with IPv6. Sure, network-enabled software might be easier to rewrite to support 40-bit IPv4+, but any hardware-accelerated products (routers, switches, network cards, etc.) would still need replacement (just as with IPv6), and you'd still need everyone to be assigned unique IPv4+ addresses in order to communicate with each other (just as with IPv6)."[0]

0: https://news.ycombinator.com/item?id=37120422

The only solution is a gov't mandate. China went from almost no adoption to leading the world in adoption (77% of all Chinese internet users) in a few years because they explicitly prioritized it in their last 5-year-plan.

The ISPs aren't gonna do it on their own.

Circa 1999 I was working for Cisco as a sysadmin. I got my CCNP through internal training and considered making a career of network administration, but ipv6 changed my mind. It seemed so much more difficult and unpleasant to deal with. I didn't want that to be my day to day work.

I think the same thing happens on a different scale with ISPs. They don't want to deal with it until they have to for largely the same reason.

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.

IPv6's failure was mostly caused by the IETF's ivory tower dwellers, who seem to generally have no practical experience or understanding whatsoever of how networks are actually built and run today, especially at the small to mid scale.

Small site multihoming, for example, is an absolute disaster. Good luck if you're trying to add a cellular backup to your residential DSL connection.

IETF says you should either have multiple routers advertising multiple provider-assigned prefixes (a manageability nightmare), or that you should run BGP with provider independent address space; have fun getting your residential ISP or cellular carrier onboard with this idea.

ipv6 adoption is still steadily rising. Not as fast as anyone hoped, but at least steadily. There is no way it can be abandoned at this point even if we wanted to.

Stripped of all the other baggage that came with it (e.g. SLAAC, IPsec, etc) IPv6 is an incredibly conservative addressing extension. The only thing even more conservative than v6 would have been to drop the lower 64 bits of the address and the associated EUI-64 local addressing scheme. Which... to be fair, that turned out to be a very bad idea, but the length of the field isn't what was holding up v6 adoption.

I suspect by "incredibly conservative" you mean "backwards compatible", which... no. You can't make an addressing extension backwards compatible with hardware that doesn't read all of the address. Of course, we did that anyway with CGNAT, and predictably it causes huge problems with end-to-end connectivity, which is the whole point of IPv6. You're probably thinking more along the lines of an explicit "extension addressing header" for v4. Problem is, that'd mean a more awkward version of IPv6's /64 address split[0], combined with all sorts of annoying connectivity problems. The same corporate middleboxes that refuse to upgrade to IPv6 also choke on anything that isn't TCP traffic to ports 80 and 443. So you'd need Happy Eyeballs style racing between CGNAT IPv4 and "extended IPv4".

Also, that would just be a worse version of 6in4. Because they also thought of just tunneling IPv6 traffic in IPv4 links. I don't think you understand how incredibly conservative IPv6 actually is.

The problem with "incredibly conservative" IP extensions is that nothing beats the conservatism of doing literally nothing. IT infrastructure is never ripped out and replaced unless there is a business case for doing so. The current problem with IPv6 adoption is that nobody has yet said "let's stop processing IPv4 traffic", they've only said "let's get more dual-stack hosts online", which is a process that only asymptotes to 100% IPv6, and never reaches it.

IPv4 was not the first version of the Internet protocol. That honor goes to Network Control Protocol (NCP). The reason why we don't have an asymptotic long tail of Internet hosts still demanding NCP connectivity is because this was back when "having a connection to the Internet" meant "having a connection to ARPANET". The US military could just refuse to process NCP packets and actively did this to force people onto IPv4. Now imagine if someone big like Google said "we're going to stop accepting IPv4 connections" - people would jump onto v6 immediately.

[0] Let's say we add a 32-bit extension header onto IPv4