[convolvatron]

I agree with you about the embedded addresses, and I don't understand why the space was moved to all zeros to a bunch of other mappings.

but the utility of this isn't that high. we already know how to handle 4-4 and 6-6 traffic just fine. but if a 4 host wants to talk to a 6 host, it just doesn't have the extra bits in order to describe it, so this just doesn't facilitate 4-6 endpoint communication at all. this is true even you substitute v6 with any other layer 3 with a larger address space.

where it does help is in a unified routing backbone, that would allow v4 prefixes to be announced in the v6 routing system. which is arguably useful.