Protocol 41
6in4
Hurricane Electric’s IPv6 Tunnel Broker uses this protocol. The prefix allocated is owned by the SP.
6rd
An SP could set up 6rd Border Relays that is delegated a 6rd prefix. The prefix is owned by the SP.
6to4
6to4 addresses starts with 2002:, followed by the IPv4 address of its router. The prefix is announced by multiple ASes.
Teredo
Teredo addresses starts with 2001:0000:. The prefix is announced by multiple ASes.