Section: 4.25.3 NIDD Configuration
Content: Figure 4.25.3-1 illustrates the procedure for configuring necessary information for data delivery via the NIDD API. The NIDD Configuration procedure can be NEF initiated or AF triggered: in the former case the procedure starts at step 1, in the latter case it starts at step 2. Figure 4.25.3-1: NIDD Configuration procedure 1. [Optional] If the NEF requires a NIDD configuration with a given AF, then the NEF sends a Nnef_NIDDConfiguration_TriggerNotify (GPSI, AF Identifier, NEF ID) message to the AF for asking the Nnef_NIDDConfiguration_Create Request for the UE identified by the GPSI. 2. The AF sends a Nnef_NIDDConfiguration_Create Request message (GPSI or External Group Identifier, AF Identifier, NIDD Duration, T8 Destination Address, Requested Action, TLTRI, Reliable Data Service Configuration, MTC Provider Information) to the NEF. Reliable Data Service Configuration is an optional parameter that is used to configure the Reliable Data Service (as defined in clause 5.31.6 of TS 23.501[ System architecture for the 5G System (5GS) ]  [2]) including port numbers for originator application(s) and receiver application(s). TLTRI is included in the request if the Requested Action is set to "Update" or "Cancel", otherwise TLTRI is not included in the request and the NEF assigns a TLTRI to the NIDD Configuration. If Reliable Data Service Configuration is present, the Reliable Data Service Configuration may include the mobile terminated and mobile originated serialization format(s) that are supported by the AF for each port number. NOTE 1: It is up to the AF to determine whether and if NIDD Duration can be set to never expire. NOTE 2: The AF is expected to be configured to use the same NEF as the one selected by the SMF during the UE's establishment of the PDU Session used for NEF based NIDD. NOTE 3: When more than one AF is associated with a PDU Session, the parameters that are provided in step 2 can be provisioned in the NEF based on operator policy or configuration. In which case, any parameters that are provided in step 2 that conflict with the provisioned values are ignored. NOTE 4: If the AF does not indicate a serialization format, it is assumed that the UE application is provisioned to know what serialization format will be used for MT traffic or that the AF will use the same format that is used by the associated MO traffic. 3. If the Requested Action is set to "Cancel" it indicates that the purpose of the request is to cancel the transaction identified by TLTRI and the flow proceeds to step 7. If the Requested Action is set to "Update", the purpose of the transaction is to update the parameters associated with the configuration (i.e. Reliable Data Service). Otherwise, the request is for a new NIDD configuration and the NEF stores the received GPSI or External Group Identifier, AF Identifier, T8 Destination Address and NIDD Duration. If either the AF is not authorised to perform this request (e.g. based on policies, if the SLA does not allow for it) or the Nnef_NIDDConfiguration_Create Request is malformed, the NEF performs step 7 and provides a Cause value appropriately indicating the error. Depending on the configuration, the NEF may change the NIDD Duration. 4. The NEF sends an Nudm_NIDDAuthorisation_Get Request (GPSI or External Group Identifier, S-NSSAI, DNN, AF Identifier, MTC Provider Information, NIDD Duration, Update Notification Address) message to the UDM to authorise the NIDD configuration request for the received External Group Identifier or GPSI. NOTE 5: The NEF uses the AF Identifier, External Group Identifier or GPSI that was obtained in step 2 to determine what DNN will be used to enable transfer of unstructured data between the UE and the AF. This determination is based on local policies. NOTE 6: The MTC Provider Information in step 2 is an optional parameter. The NEF should validate the provided MTC Provider Information and may override it to a NEF selected MTC Provider Information based on configuration. How the NEF determines the MTC Provider Information, if not present in step 2, is left to implementation (e.g. based on the requesting AF). 5. The UDM examines the Nudm_NIDDAuthorisation_Get Request message. If the authorisation is successful and if an External Group Identifier was included in step 4, the UDM maps the External Group Identifier to an Internal-Group Identifier and a list of GPSIs and maps GPSIs to SUPIs. NOTE 7: If External Group Identifier was included in step 4, how the UDM selects a GPSI when multiple GPSIs are associated with the same SUPI is left to implementation, e.g. based on the MTC Provider Information (if received) or the default GPSI (if not received). 6. The UDM sends an Nudm_NIDDAuthorisation_Get Response (single value or list of (SUPI and GPSI), Result) message to the NEF to acknowledge acceptance of the Nudm_NIDDAuthorisation_Get Request. If the UDM determines that the list size exceeds the message capacity, the UDM shall segment the list and send it in multiple messages (for details on segmentation, see TS 29.503[ 5G System; Unified Data Management Services; Stage 3 ]  [52]). The SUPI(s) and if available, the GPSI(s) (when Nnef_NIDDConfiguration_Create Request contains an GPSI) are returned by the UDM in this response. This allows the NEF to correlate the AF request received in step 2 of this procedure with the SMF-NEF Connection to be established for each UE or each group member UE. Depending on the configuration (e.g. based on DNN), the UDM may change the NIDD Duration and include the updated value of the NIDD Duration in the response to the NEF. 7. The NEF sends a Nnef_NIDDConfiguration_Create Response (TLTRI, Maximum Packet Size, Reliable Data Service Indication and Cause) message to the AF to acknowledge acceptance of the Nnef_NIDDConfiguration_Create Request. If the NIDD Configuration was accepted, the NEF assigns a TLTRI to the NIDD Configuration and sends it to the AF. The NEF creates an association between the TLTRI, GPSI or External Group Identifier, SUPI and PDU session ID which is received from the SMF in step 2 of the SMF-NEF Connection procedure in clause 4.25.1. In the MT NIDD procedure, the NEF will use TLTRI and either GPSI or External Group Identifier to determine the SUPI(s) and PDU session ID(s) of PDU Session(s) for delivering unstructured data. In the MO NIDD procedure, the NEF will use the SUPI(s) and PDU session ID(s) to obtain the TLTRI, GPSI. The Reliable Data Service Indication indicates if the Reliable Data Service is enabled in the NIDD configuration. The Maximum Packet Size is the maximum NIDD packet size. The response may include an updated value of the NIDD Duration.