I was reading the requirements draft today, and I noticed this:
I'm not sure this requirement makes a lot of sense. An IPv4-only node clearly does not have any Mobile IPv6 code in it. Even if by some magic the RO packets were made to go through the NAT, the peer would drop them on the floor :-)I5: MIPv6 support The translation mechanism SHOULD not prevent MIPv6 Route Optimization when the CN is a v4-only node
I actually believe R3 (allowing the use of native connectivity when dual-stack is available) already covers most of what we want to say about mobility in this context. That is, the NATted path should not take precedence over the native IPv6 path, because otherwise many things currently possible in IPv6 no longer work.
I don't know if you want to remove I5 altogether or consider saying something else. There is a need to allow two dual-stack hosts, one in v6-only network and the other in a v4-only network, to be able to use Mobile IPv6 route optimization with each other. But I don't know if our future NAT spec needs to include that, or if its simply an additional scenario for the Mobile IPv6 Dual Stack spec. That spec already allows a dual-stack mobile node to connect to its home agent over v4-only networks.
Jari