[fpoling]

Even 15 years ago IPv6 was much worse than IPv4 for most of the people. Only when the mobile operators has started to insist on it then the usage started to grow to significant numbers. Which showed the real problem with IPv6: lack of compatibility with IPv4. That was absolutely possible 30 years ago, but the designers decided that it would just complicate things.

[orangeboats]

I am tired of people claiming that you can make a "new Internet protocol that is compatible with IPv4".

No, backwards compatibility is not the problem here: IPv6-only hosts can easily connect to IPv4 hosts. Just append "64:ff9b::" to an existing IPv4 address, like so: 64:ff9b::8.8.8.8. Even prior to NAT64, we have plenty of schemes like 6to4 to bridge IPv4 and IPv6.

But no IPv4 hosts can ever connect to IPv6 hosts, or IPv7, or IPvInfinite for that matter. I will refer to my previous comment on why that is: https://news.ycombinator.com/item?id=46469336

[positr0n]

I think the people complaining about compatibility are more talking about the concepts in IPv4 and IPv6. IPv6 could have been "everything is the same except the IP address is 16 bytes instead of 4". Instead there are new ways to do everything.

Addressing works differently (no broadcast, multicast everywhere, link-local is mandatory). Configuration works differently (SLAAC, RA, DHCPv6 is not a drop-in replacement for regular DHCP). Neighbor discovery replaces ARP and depends on ICMPv6 working. Fragmentation behavior changed. NAT is “not a thing” by design, which breaks a bunch of assumptions people built entire networks around.

[Dagger2]

No they didn't? v6 is compatible with v4 in tons of different ways, probably in almost every way that it's possible to be compatible with v4.

Admittedly, it's not compatible in the ways that _aren't_ possible. But it's highly unreasonable to blame that on the people who designed v6.