Heavy use of tunnelling

There are numerous RFC for IPv6 transition technologies that use IPv6-over-IPv4 tunnel
RFC1933/2893 configured tunnel
RFC1933/2893 automatic tunnel
RFC2401 IPsec tunnel
RFC2473 IPv6 generic packet tunnelling
RFC2529 6over4 tunnel
RFC3056 6to4 tunnel
isatap tunnel
mobile-ip6 (uses RFC2473)
Difficult to filter/police

Solution: construct simple network
RFC1933/2893 configured tunnel will suffice
Other transition technologies are frills