[Spivak]

> IPv6 just works

Only via the herculean efforts of a bunch of people having to literally reinvent the world to deal with it. Everything needs IPv6 support specifically. It's such a mess, if IPv6 has just been identical to IPv4 but with larger addresses we would be on it by now. But no they had to make it their religious crusade to eliminate NAT (and now we have NAT66 so clearly a winner) put IPSec in there which is hilarious in the era of Wireguard and eliminate DHCP which is actually insane and makes a stupid number of assumptions about hosts being able to communicate with one another and actually complicates DNS registration.

Can you imagine how trivial it would have been if you could support both v4 and v6 by just supporting v6 and having 0::v4addr be literally equivalent to ipv4? It would be more difficult to not support v6.

[Dylan16807]

> Can you imagine how trivial it would have been if you could support both v4 and v6 by just supporting v6 and having 0::v4addr be literally equivalent to ipv4? It would be more difficult to not support v6.

And how are you supposed to get the packets back when the client has an address outside that range? You still need to add support everywhere, or have NAT gateways into the areas that lack support.

Automatic mapping of IPv4 addresses exists but it requires support infrastructure just as much as any other method of allowing access to IPv4 devices.

[SoftTalker]

Yes I'm not qualified to really argue the point but naively it never made sense to me that IPv4 was not backwards compatible with IPv6 addressing. You'd think the people on the committees would have foreseen the trouble that would avoid. Telephone companies didn't make you dial the area code for local numbers. Microsoft bent over backwards to make sure that old DOS software still worked on Windows. Linux has a mandate to never break userland. This is not an unfamiliar concept.

[p1mrx]

IP is a bidirectional protocol, so the correct analogy would be if Microsoft had to make DOS software run on Windows, and Windows software run on DOS.

Remember the error "This program cannot be run in DOS mode"?

IPv4 and IPv6 are unidirectionally compatible using NAT64. The fact that you can make an IPv6 to IPv4 TLS connection using a packet-level translator without breaking the endpoints is quite remarkable, and it wouldn't have been possible if the protocols were too dissimilar.

[dilyevsky]

Hey don't forget about NDP and weird ULA thing which is kinda like private but global.

[Spivak]

Oh god how could I forget the "let's just replace ARP and make people using LVS and keepalived change their setups."

What you need to support dual stack? Who would do that…