10. Identity Association

10. Identity Association

An "Identity Association" (IA) is a construct through which a server and a client can identify, group, and manage a set of related IPv6 addresses. Each IA consists of an IAID and associated configuration information.

A client MUST associate at least one distinct IA with each of its network interfaces for which the client wants to request assignment of IPv6 addresses from a DHCP server. The client uses the IA assigned to an interface to obtain configuration information for that interface from the server. Each IA MUST be associated with exactly one interface.

The IAID uniquely identifies the IA and MUST be chosen to be unique among the IAIDs for all IAs on that client. The IAID is chosen by the client. For any given use of an IA by the client, the IAID for that IA MUST be consistent across DHCP client restarts. The client can maintain consistency by storing the IAID in non-volatile storage or by using an algorithm that will consistently produce the same IAID as long as the client's configuration has not changed. If the client has no non-volatile storage and the client's hardware configuration changes, the client may not be able to maintain consistency of the IAID.

The configuration information in an IA consists of one or more IPv6 addresses and the times T1 and T2 for the IA. For the representation of IAs in DHCP messages, see section 22.4.

Each address in an IA has a preferred lifetime and a valid lifetime, as defined in RFC 2462 [RFC 2462]. The lifetimes are transmitted from the DHCP server to the client through IA options. The lifetimes apply to the use of IPv6 addresses, as described in section 5.5.4 of RFC 2462.