Section: 5.2.3.2.1 Nudm_UECM_Registration service operation
Content: Service operation name: Nudm_UECM_Registration Description: Register UE's serving NF (if NF Type is AMF, SMSF, or NWDAF) or Session's serving NF (if NF Type is SMF) on the UDM. This operation implies the following: - The authorization, if applicable, to register the NF service consumer in UDM for the UE (e.g. based on UE roaming/RAT restrictions applicable when NF type is AMF). If this is successful, the NF service consumer is set as a serving NF for the corresponding UE/Session context. - When the consumer is AMF or SMF, it is implicitly subscribed to be notified when it is deregistered in UDM. This notification is done by means of Nudm_UECM_DeregistrationNotification operation. - When the consumer is AMF or SMF, it may optionally use this operation to subscribe to be notified of the need for P-CSCF Restoration. This notification is done by means of Nudm_UECM_PCscfRestoration operation. For more information regarding P-CSCF restoration procedures see TS 23.380[ IMS Restoration Procedures ]  [38]. Inputs, Required: NF ID, SUPI, NF Type, Access Type (if NF Type is AMF, SMSF), RAT Type and GUAMI (if NF Type is AMF), PDU Session ID (if NF Type is SMF), Analytics ID(s) (if NF Type is NWDAF). If NF Type is SMF: DNN or Indication of Emergency Services, S-NSSAI, SMF+PGW-C FQDN for S5/S8 if the PDU Session supports EPS interworking, Serving Node PLMN ID. If NF type is AMF and Access Type is 3GPP access: Registration type. If NF type is SMSF: SMSF MAP address and/or Diameter address, Serving PLMN ID. NOTE: The GUAMI includes the MNC+MCC of the serving PLMN. In home routed roaming, the H-SMF provides the PLMN ID of the HPLMN as Serving Node PLMN ID. In LBO roaming, the SMF in the VPLMN provides the PLMN ID of the serving PLMN in the VPLMN as Serving Node PLMN ID. Inputs, Optional: PEI (conditional, condition stated below), P-CSCF Restoration notification information, NID (e.g. if NF Type is AMF; see clause 5.18 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]), backup AMF(s) (if NF Type is AMF), "Homogeneous Support of IMS Voice over PS Sessions" indication (if NF Type is AMF), UE SRVCC capability (if NF Type is AMF), indication that access is from ePDG (shall be sent if NF Type is SMF and PDU Session is setup via S2b), VGMLC ID (if NF type is AMF and information is available in AMF). Backup AMF(s) sent only once by the AMF to the UDM in its first interaction with the UDM, indication of no event exposure subscription information available (if NF Type is AMF). PCF ID selected for the PDN connection/PDU Session (If NF type is SMF), UE MINT support indicator, Disaster Roaming indicator indicating that Disaster Roaming service is applied. Outputs, Required: Result indication. Outputs, Optional: None. If the PEI was retrieved by the AMF (either from the UE or another AMF), AMF shall provide it to the UDM using Nudm_UECM_Registration in order to ensure that the UDM always has the latest PEI available e.g. for reporting event Change of SUPI-PEI association. See step 14a of clause 4.2.2.2.2 for an example usage of this service operation.