[cesarb]

> If they simply added two top octets, saying that 0.0.... was the old ipv4, everyone would have used it ages ago.

How would you "simply add two top octets"? The address fields in the IPv4 header are a fixed size of 32 bits. Every time this is discussed, someone comes up with this suggestion to "just make the addresses longer and change nothing else", but there's no way to make the addresses longer without changing something else. And that's before considering compatibility with older hosts or routers; how would an old host talk to a new host, or two new hosts talk one to another with an old router in the path? In the end, what you'd have would be two separate networks, with some hosts being in both networks, which is exactly what we have with IPv4 and IPv6.

[yjftsjthsd-h]

Yes, obviously you need a new wire format and bigger addresses; that was always going to change. What did not need to happen was changing/replacing DHCP, routing changes, and a half-hearted attempt to bake in IPsec.