What changes exactly makes it orders of magnitudes more difficult?
And that's not even beginning to talk about supporting services such as RA, etc.
IPv6 has been available much longer than IPv4 was when the Internet went mainstream in the mid 90's. Yes, it's work to deploy. You might need to even upgrade to a router built in the past 10 years. Organizations have had decades to learn about it and deploy it. People just don't like change... especially corporate IT departments.
Well, all change causes pain. People don't like change when there isn't an obvious benefit to offset the pain it brings. When they do see the benefit, though, they tend to embrace change. I think the mistake that was made with IPv6 was a social one: it's a huge amount of change (pain) for a benefit that is invisible or irrelevant to a whole lot of people.
IT departments, like most departments, dislike expense more than they dislike change.
In reading the discussions leading up to IPv6, it was clear that the actual experts involved saw a few ways to maintain such compatibility. It was decided not to do that, though, because tradeoffs are (as always) involved. There are features they wanted to include that wouldn't have been possible while maintaining compatibility, and it was thought that a breaking change was worthwhile now as long as the IPv6 protocol was good enough that no breaking change would be required in the future.
For applications a subset of the IPv6 address space is set aside for IPv4 connections. So applications only need to support IPv6 and can communicate with IPv4 destinations using ::ffff:<ipv4-address>, so for example ::ffff:8.8.8.8 is a valid ipv6 address. But that still requires the host to have a IPv4 address for this to work (it's only so applications can support both while only requiring support for one address family).
For IPv6 hosts connecting to IPv4 hosts there are different methods that translate IPv6 to IPv4 (NAT64, SIIT, etc.), but most (if not all) just embed the whole IPv4 address space inside IPv6 (and again you can have something like 2001:db8::8.8.8.8) and then translate based on extracting the IPv4 address from the IPv6 address. And in combination with DNS64 you can have ipv6-only hosts that can communicate just fine with IPv4-only hosts (all ipv4 traffic gets routed via NAT64).
The problem is however the inverse. IPv4 is not forward-compatible. A IPv4-only host can only ever form outgoing connections to other IPv4 hosts, since there is no way to put more than 32-bits of information into the 32-bit destination field of the IPv4-packet. You can of course expose certain ipv6-only hosts to the ipv4-internet using for example SIIT, but that requires a 1:1 mapping between the IPv4 and IPv6 host. If you don't have that explicit mapping, how would a gateway know which IPv6 address you meant?
Every time IPv6 negativists come to the thread they make it look like you need to be a rocket scientist to configure two hosts for IPv6.
> You can't incrementally shift toward IPv6
Yes, you can, you don't need to throw out your lovely IPv4 networks and addresses. Yes, it's dual-stack.
> you have to run [..] tunnel, which adds at least another layer of complexity to everything
No more complexity than running a PPPoE/PPTP tunnel to get IPv4 connectivity.
> And that's not even beginning to talk about supporting services such as RA, etc.
Oh God! You need to read another 20 pages on top of the previous 20 pages you read to understand IPv6! So, so hard!
BTW you obviously forgot what there was a time when you didn't know nothing about IPv4, including what is the default router, what is ARP, what is CIDR, netmask, routing etc, etc. Yet somehow you know that now. Same applies to IPv6. You had 20 years to learn it, yet in 2023 you still complaining what to use a technology you need to learn.
I'm describing various reasons why there is such slow adoption of IPv6. Ridiculing and being mad at people for avoiding it isn't likely to make them feel any differently. Understanding the resistance might be helpful in terms of getting people over that hump.
You are not a devil's advocate nor a public defender, yet you defend those people, using the same nonsense reasons they use to defend their position.
> I'm describing various reasons why there is such slow adoption of IPv6.
For the most part those reasons boils down to 'I have my way and don't do a shit to learn something new'.
> Ridiculing
Yes, they deserve it.
> and being mad at people
A grown-ass person who can't find the reason and time to learn something new? I'm not mad at them, but I don't like when people defend them.
> Understanding the resistance might be helpful in terms of getting people over that hump.
See 'I have my way' part above.