6.3. IPv6 Prefix Handling

6.3. IPv6 Prefix Handling

There are two relevant IPv6 prefixes that the CLAT must be aware of.

First, CLAT must know its own IPv6 prefixes. The CLAT should acquire a /64 for the uplink interface, a /64 for all downlink interfaces, and a dedicated /64 prefix for the purpose of sending and receiving statelessly translated packets. When a dedicated /64 prefix is not available for translation from DHCPv6-PD [RFC3633], the CLAT may perform NAT44 for all IPv4 LAN packets so that all the LAN-originated IPv4 packets appear from a single IPv4 address and are then statelessly translated to one interface IPv6 address that is claimed by the CLAT via the Neighbor Discovery Protocol (NDP) and defended with Duplicate Address Detection (DAD).

Second, the CLAT must discover the PLAT-side translation IPv6 prefix used as a destination of the PLAT. The CLAT will use this prefix as the destination of all translation packets that require stateful translation to the IPv4 Internet. It may discover the PLAT-side translation prefix using [Discovery-Heuristic]. In the future, some other mechanisms, such as a new DHCPv6 option, will possibly be defined to communicate the PLAT-side translation prefix.