Content for  TS 23.122  Word version:  18.6.0

The SOR-AF to the UDM: Nudm_ParameterProvision_Update request is sent to the UDM to trigger the update of the UE with the SOR-SNPN-SI or SOR-SNPN-SI-LS.

The UDM to the AMF: The UDM notifies the changes of the user profile to the affected AMF by the means of invoking Nudm_SDM_Notification service operation. The Nudm_SDM_Notification service operation contains the steering of roaming information that needs to be delivered transparently to the UE over NAS within the Access and Mobility Subscription data. If the HPLMN or subscribed SNPN decided that the UE is to acknowledge successful security check of the received steering of roaming information, the Nudm_SDM_Notification service operation also contains an indication that the UDM requests an acknowledgement from the UE as part of the steering of roaming information. Upon receiving the SOR-SNPN-SI or the SOR-SNPN-SI-LS, the UDM shall include the SOR-SNPN-SI (if any), SOR-SNPN-SI-LS (if any), and the HPLMN indication that 'no change of the "Operator Controlled PLMN Selector with Access Technology" list stored in the UE is needed and thus no list of preferred PLMN/access technology combinations is provided'.

The AMF to the UE: the AMF sends a DL NAS TRANSPORT message to the served UE. The AMF includes in the DL NAS TRANSPORT message the steering of roaming information received from the UDM.

Upon receiving the steering of roaming information containing the SOR-SNPN-SI (if any), the SOR-SNPN-SI-LS (if any), and the HPLMN indication that 'no change of the "Operator Controlled PLMN Selector with Access Technology" list stored in the UE is needed and thus no list of preferred PLMN/access technology combinations is provided', the UE shall perform a security check on the steering of roaming information included in the DL NAS TRANSPORT message to verify that the steering of roaming information is provided by HPLMN, and:

1. if the security check is successful, then:
   • the ME shall replace the credentials holder controlled prioritized list of preferred SNPNs for the selected PLMN subscription with the received credentials holder controlled prioritized list of preferred SNPNs, if any, the ME shall replace the credentials holder controlled prioritized list of GINs for the selected PLMN subscription with the received credentials holder controlled prioritized list of GINs, if any, and the ME shall delete the SNPNs identified by the credentials holder controlled prioritized list of preferred SNPNs or the SNPN(s) stored along with GIN(s) identified by the credentials holder controlled prioritized list of GINs from the list of "temporarily forbidden SNPNs" and the list of "permanently forbidden SNPNs", if they are present in these lists: and
   • the ME shall replace the "credentials holder controlled prioritized list of preferred SNPNs for access for localized services in SNPN" for the selected PLMN subscription with the received "credentials holder controlled prioritized list of preferred SNPNs for access for localized services in SNPN", if any, the ME shall replace the "credentials holder controlled prioritized list of preferred GINs for access for localized services in SNPN" for the selected PLMN subscription with the received "credentials holder controlled prioritized list of preferred GINs for access for localized services in SNPN", if any, and the ME shall delete the SNPNs identified by the "credentials holder controlled prioritized list of preferred SNPNs for access for localized services in SNPN" or the SNPN(s) stored along with GIN(s) identified by the "credentials holder controlled prioritized list of preferred GINs for access for localized services in SNPN" from the list of "temporarily forbidden SNPNs for access for localized services in SNPN" and the list of "permanently forbidden SNPNs for access for localized services in SNPN", if they are present in these lists.
   If the UDM has requested an acknowledgement from the UE in the DL NAS TRANSPORT message, the UE sends an UL NAS TRANSPORT message to the serving AMF with an SOR transparent container including the UE acknowledgement and the UE shall set:
   • the "ME support of SOR-SNPN-SI" indicator to "supported"; and
   • the "ME support of SOR-SNPN-SI-LS" indicator to "supported" if the UE supports access to an SNPN providing access for localized services in SNPN.
   If the UDM has not requested an acknowledgement from the UE then step 5 is skipped; and
2. if the selected PLMN is a VPLMN, the security check is not successful and the UE is in automatic network, then
   • if the UE has a stored SOR-CMCI, then:
     • if there are ongoing PDU sessions or services, the current PLMN is considered as lowest priority and the UE shall apply the actions in clause C.4.2;
     • if there are no ongoing PDU sessions or services, the UE shall release the current N1 NAS signalling connection locally and attempt to obtain service on a higher priority PLMN as specified in clause 4.9.3, with an exception that the current PLMN is considered as lowest priority;
   • if the UE does not have a SOR-CMCI stored in the non-volatile memory of the ME, then:
     • if there are ongoing PDU sessions or services, the UE shall wait until it moves to idle mode or 5GMM-CONNECTED mode with RRC inactive indication (see TS 24.501) before attempting to obtain service on a higher priority PLMN as specified in clause 4.4.3.3 by acting as if timer T that controls periodic attempts has expired, with an exception that the current PLMN is considered as lowest priority. If the selected PLMN is a VPLMN and the UE has an established emergency PDU session then the UE shall attempt to perform the PLMN selection after the emergency PDU session is released and after the UE enters idle mode or 5GMM-CONNECTED mode with RRC inactive indication (see TS 24.501); or
     • if there are no ongoing PDU sessions or services, the UE shall release the current N1 NAS signalling connection locally and attempt to obtain service on a higher priority PLMN as specified in clause 4.9.3, with an exception that the current PLMN is considered as lowest priority.
   Step 5 is skipped;

The AMF to the UDM: If the UL NAS TRANSPORT message with an SOR transparent container is received, the AMF uses the Nudm_SDM_Info service operation to provide the received SOR transparent container to the UDM. If the HPLMN decided that the UE is to acknowledge successful security check of the received steering of roaming information in step 2, the UDM verifies that the acknowledgement is provided by the UE. The UDM shall store the "ME support of SOR-SNPN-SI" indicator. If the "ME support of SOR-SNPN-SI-LS" indicator in the header of the SOR transparent container is set to "supported", then the UDM shall store the "ME support of SOR-SNPN-SI-LS" indicator, otherwise the UDM shall delete the stored "ME support of SOR-SNPN-SI-LS" indicator, if any. If the present flow was invoked by the UDM after receiving from the SOR-AF the SOR-SNPN-SI or the SOR-SNPN-SI-LS for a UE identified by SUPI using an Nudm_ParameterProvision_Update request, and the UDM verification of the UE acknowledgement is successful, then the UDM informs the SOR-AF about successful delivery of the SOR-SNPN-SI or the SOR-SNPN-SI-LS using Nsoraf_SoR_Info (SUPI of the UE, successful delivery); and

The UDM to the SOR-AF: Nsoraf_SoR_Info (SUPI of the UE, successful delivery, "ME support of SOR-SNPN-SI" indicator, "ME support of SOR-SNPN-SI-LS" indicator, if any). If the HPLMN policy for the SOR-AF invocation is present and the HPLMN UDM received and verified the UE acknowledgement in step 5, then the UDM informs the SOR-AF about successful delivery of the SOR-SNPN-SI or the SOR-SNPN-SI-LS to the UE. The UDM shall include the "ME support of SOR-SNPN-SI" indicator. If the "ME support of SOR-SNPN-SI-LS" indicator is stored for the UE, the UDM shall include the "ME support of SOR-SNPN-SI-LS" indicator..