v6ops-nat64-pb-statement-req: MIPv6 RO requirement

[Thomas Narten <narten@us.ibm.com>]

draft-ietf-v6ops-nat64-pb-statement-req-00.txt says:

>    I5: MIPv6 support
> 
>    The translation mechanism SHOULD not prevent MIPv6 Route Optimization
>    when the CN is a v4-only node

What exactly is meant by this? Is the intention that a MIPv6 MN should
be able to use RO with an IPv4-only CN?

To invoke MIPv6 RO, the CN must actively participate in the
signalling. Presumably, an IPv4-only node doesn't implement MIPv6 at
all.

What exactly is this requirement intended to achieve?

Thomas