[Conditional] new AMF to UE: Identity Request/Response (PEI).
If the PEI was not provided by the UE nor retrieved from the old AMF the Identity Request procedure is initiated by AMF sending an Identity Request message to the UE to retrieve the PEI. The PEI shall be transferred encrypted unless the UE performs Emergency Registration and cannot be authenticated.
For an Emergency Registration, the UE may have included the PEI in the Registration Request. If so, the PEI retrieval is skipped.