IPv6 Neighbor Discovery Protocol Extensions
Inverse Neighbor Discovery (IND) allows nodes to determine and advertise an IPv6 address corresponding to a given MAC address. This is similar to Reverse ARP for IPv4. This is an extension to the IPv6 NDP and is defined in RFC 3122.
Secure Neighbor Discovery Protocol (SEND) is also an extension of NDP delivering security features to such communication. This is defined in RFC3971 and has been updated in RFC 6494.