L.6 Address and identity management concepts

23.2283GPPIP Multimedia Subsystem (IMS)Release 18Stage 2TS

L.6.1 Deriving IMS identifiers

ISIM is the primary source for IMS identity information. If an ISIM is not present, the UE shall use the IMS credentials stored in the IMC to access IMS.

If no IMS credentials are stored in the IMC, then temporary credentials shall be derived as follows:

– a Temporary Private User Identity shall be derived from the Mobile Station ID (IMSI, MIN or IRM), which allows for uniquely identifying the user within the operator’s network;

– a Temporary Public User Identity shall be derived from the MSID, and shall be used in SIP registration procedures. The Temporary Public User Identity shall take the form of a SIP URI (as defined in RFC 3261 [12] and RFC 3986 [13]).

It is strongly recommended that the Temporary Public User Identity is set to barred for SIP non-registration procedures. The following applies if the Temporary Public User Identity is barred:

– A Temporary Public User Identity shall not be displayed to the user and shall not be used for public usage such as displaying on a business card.

– The Temporary Public User Identity shall only be used during the SIP initial registration, re-registration and mobile initiated de-registration procedures.

– The implicitly registered Public User Identities shall be used for session handling, in non-registration SIP messages and may be used at subsequent SIP registration procedures.

– A Temporary Public User Identity shall only be available to the CSCF and HSS nodes.

NOTE: If a Temporary Public Identity is used, the user can not initiate any sessions until the implicitly registered public identities are available in the UE.

When a Temporary Public Identity has been used to register an IMS user, the implicit registration will ensure that the UE, P‑CSCF & S‑CSCF have Public User Identity(s) for all IMS procedures after the initial registration has been completed.