6. Identity Association for Prefix Delegation

6. Identity Association for Prefix Delegation

An IA_PD is a construct through which a delegating router and a requesting router can identify, group and manage a set of related IPv6 prefixes. Each IA_PD consists of an IAID and associated configuration information. An IA_PD for prefixes is the equivalent of an IA (described in RFC 3315) for addresses.

An IA_PD is different from an IA, in that it does not need to be associated with exactly one interface. One IA_PD can be associated with the requesting router, with a set of interfaces or with exactly one interface. A requesting router must create at least one distinct IA_PD. It may associate a distinct IA_PD with each of its downstream network interfaces and use that IA_PD to obtain a prefix for that interface from the delegating router.

The IAID uniquely identifies the IA_PD and must be chosen to be unique among the IA_PD IAIDs on the requesting router. The IAID is chosen by the requesting router. For any given use of an IA_PD by the requesting router, the IAID for that IA_PD MUST be consistent across restarts of the requesting router. The requesting router may maintain consistency either by storing the IAID in non-volatile storage or by using an algorithm that will consistently produce the same IAID as long as the configuration of the requesting router has not changed. If the requesting router uses only one IAID, it can use a well-known value, e.g., zero.

The configuration information in an IA_PD consists of one or more IPv6 prefixes along with the times T1 and T2 for the IA_PD. See section 9 for the representation of an IA_PD in a DHCP message.