IPv6 extension headers & IPv4 options
IPsec: havent tried!
- might be possible as the translator doesnt modify anything above the logical IP layer
Authentication header hard to translate
- could carry fragmentation information end-to-end for AH using IPv6 fragment header, but then break other semantics
- have to change how IPv4 and IPv6 currently compute auth. info
IPv6 can encapsulate more options than the IPv4 limit of 40 bytes
IPv6 Extended Routing extensions is a superset of the IPv4 feature domain -- not sure if it makes sense to do source routing through a translator.