Sounds like this is exactly that. Too bad they didn't do that first, and we've had a couple decades of failing to widely adopt IPv6 because it's too complicated and confusing.
"1.7. Backward Compatibility and Transition
IPv4 is a proper subset of IPv8:
IPv8 address with r.r.r.r = 0.0.0.0 = IPv4 address
Processed by standard IPv4 rules
No modification to IPv4 device required
No modification to IPv4 application required
No modification to IPv4 internal network required
IPv8 does not require dual-stack operation. There is no flag day. 8to4 tunnelling enables IPv8 islands separated by IPv4- only transit networks to communicate immediately. CF naturally incentivises IPv4 transit ASNs to upgrade by measuring higher latency on 8to4 paths -- an automatic economic signal without any mandate."
IPv6 doesn't require modifications to IPv4 devices, applications, networks etc etc either. You just cannot reach IPv6 networks and devices from them, and the same applies to IPv8. 8to4 is nothing innovative because 6to4 already exists. In the end this proposal has all the disadvantages of IPv6 with less advantages.
This is not true, and you obviously have not read the specification. In IPv8 when a station ARPs it ARPs using ARP8 and if there is no response 50ms later it ARP4. If that station replies than IPv8 sends IPv4 packets to that station for the remainder of the ARP time out session.
Except for the r.r.r.r section of the header the rest of the payload IS ipv4.
So to encapsulate between an IPv4 network and an IPv8 network all there is from 4 to 8 add 0.0.0.0 as the source, and asn as the destination. From 8 to 4 remove the 0.0.0.0 as the ASN destination and forward the IPv4 packets.
When you need to traverse from 8 to 4 (or several 4s) to an 8 each ASN has an IPv4 anycast address that is on every IPv8 router and the packets are sent to that address, allowing them to find their way through the internet without tunnels.
It is the absolute compatibility of the payload of IPv4 and IPv8 that makes this easy and teniable.
