Is there a reason why adoption has been so abysmally slow? Like surely all the big players have updated their networking equipment by now, and surely every piece of enterprise-grade kit sold in the last 20 years has supported v6.

The only arguments I've ever heard against ipv6 that made any sense are that:

1: it's hard to remember addresses, which is mayyyyybe valid for homelab enthusiast types, but for medium scale and up you ought to have a service that hands out per-machine hostnames, so the v6 address becomes merely an implementation detail that you can more or less ignore unless you're grepping logs. I have this on my home network with a whopping 15 devices, and it's easy.

and 2: with v6 you can't rely on NAT as an ersatz firewall because suddenly your printer that used to be fat dumb and happy listening on 192.168.1.42 is now accidentally globally-routable and North Korean haxors are printing black and white Kim Il Sung propaganda in your home office and using up all your toner. And while this example was clearly in jest there's a nugget of truth that if your IOT devices don't have globally-routable addresses they're a bit harder to attack, even though NAT isn't a substitute for a proper firewall.

But both of these are really only valid for DIY homelab enthusiast types. I honestly have no idea why other people resist ipv6.

The big reason is that domestic ISPs don't want to switch (not just in the US, but everywhere really.)

Data centers and most physical devices made the jump pretty early (I don't recall a time where the VPS providers I used didn't allow for IPv6 and every device I've used has allowed IPv6 in the last 2 decades besides some retro handhelds), but domestic ISPs have been lagging behind. Mobile networks are switching en masse because of them just running into internal limits of IPv4.

Domestic ISPs don't have that pressure; unlike mobile networks (where 1 connection needing an IP = 1 device), they have an extra layer in place (1 connection needing an IP = 1 router and intranet), which significantly reduces that pressure.

The lifespan of domestic ISP provided hardware is also completely unbound by anything resembling a security patch cycle, cost amortization or value depreciation. If an ISP supplies a device, unless it fundamentally breaks to a point where it quite literally doesn't work anymore (basically hardware failure), it's going to be in place forever. It took over 10 years to kill WEP in favor of WPA on consumer grade hardware. To support IPv6, domestic ISP providers need to do a mass product recall for all their ancient tech and they don't want to do that, because there's no real pressure to do it.

IPv6 exists concurrently with IPv4, so it's easier for ISPs to make anyone wanting to host things pay extra for an IPv4 address (externalizing an ever increasing cost on sysadmins as the IP space runs out of addresses) rather than upgrade the underlying tech. The internet default for user facing stuff is still IPv4, not IPv6.

If you want to force IPv6 adoption, major sites basically need to stop routing over IPv4. Let's say Google becomes inaccessible over IPv4 - I guarantee you that within a year, ISPs will suddenly see a much greater shift towards IPv6.

> 1: it's hard to remember addresses

fd::1 is perfectly valid internal IPv6 address (along with fd::2 ... fd::n)

Has it been abysmally slow? What's the par time for migrating millions of independent networks, managed by as many independent uncoordinated administrators, to a new layer 3 protocol?

We've never done this before at this scale. Maybe this is just how long it takes?

Sure, the data plane supports it - but what about the management plane?

I wouldn't be surprised if ISPs did all the management tasks through a 30-year-old homebrew pile of technical debt, with lots of things relying on basic assumptions like "every connection has exactly one ip address, which is 32 bits long".

Porting all of that to support ipv6 can easily be a multi-year project.

> Like surely all the big players have updated their networking equipment by now

My home isp can't even do symmetrical gigabit, let alone ipv6...

Ignore all the excuses like longer addresses and incompatible hardware. The actual reason is that everyone hates change.

IPv6 is a recursive WTF. It might _look_ like a conservative expansion of IPv4, but it's really not. A lot of operational experience and practices from IPv4 don't apply to IPv6.

For example, in IPv4 each host has one local net address, and the gateway uses NAT to let it speak with the Internet. Simple and clean.

In IPv6 each host has multiple global addresses. But if your global connection goes down, these addresses are supposed to be withdrawn. So your hosts can end up with _no_ addresses. ULA was invented to solve this, but the source selection rules are STILL being debated: https://www.ietf.org/archive/id/draft-ietf-6man-rfc6724-upda...

Then there's DHCP. With IPv4 the almost-universal DHCP serves as an easy way to do network inspection. With IPv6 there's literally _nothing_ similar. Stateful DHCPv6 is not supported on Android (because its engineers are hell-bent on preventing IPv6). And even when it's supported, the protocol doesn't require clients to identify themselves with a human-readable hostname.

Then there's IP fragmentation and PMTU that are a burning trash fire. Or the IPv6 extension headers. Or....

In short, there are VERY good reasons why IPv6 has been floundering.