For route optimisation, it is not encrypted, as IPsec is typically not used in the RO case.
you can use it if you want to.
If IPsec is used with RO, I don't remember what the specs say, but that doesn't currently matter much since IPsec cannot really be used with RO until MOBIKE WG produces its results.
why? MIP signaling can be used to update the tunnel end points.
I realised I was wrong some time after I sent my second message. Sorry for the confusion. Anyway, this discussion does not belong to this list as it has nothing to do with multi6.
--Pekka