6.2.4.2 Message delivery to NG-RAN

When the AIOTF sends an NGAP message, the AMF receives an Namf_AIoT_MessageDelivery request and sends the corresponding NGAP message to NG-RAN. The additional steps used for an indirect interface from an AIOTF to NG-RAN are shown in Figure 6.2.4.2-1.

1. The AIOTF sends Namf_AIoT_MessageDelivery Request message (NGAP AIoT information, NG-RAN ID, AIOTF ID, Correlation ID, AIoT NGAP Message Type, Notification endpoint, [RAN AIoT Device NGAP ID]) to the AMF.

The AIoT NGAP Message Type identifies the NGAP message to send to NG-RAN and NGAP AIoT information is provided to NG-RAN in the NGAP message. The message includes RAN AIoT Device NGAP ID if the AIoT NGAP Message Type indicates "Command Request".

2. The AMF responds to the AIOTF with a result indicating whether the AMF will handle the request. If a failure is indicated by the result indication, then the procedure stops and the remaining steps are skipped.

If the AMF accepts the request, the AMF maintains a context for the transaction including the NG-RAN ID, AIOTF ID, Correlation ID, RAN AIoT Device NGAP ID (if received) and Notification endpoint. This context is used to route multiple NGAP messages from NG-RAN to AIOTF, see clause 6.2.4.3. The AIOTF is implicitly subscribed to Namf_AIoT_Notify events.

3. The AMF sends an NGAP message (AIOTF ID, Correlation ID, NGAP AIoT information, [RAN AIoT Device NGAP ID]) to the target NG-RAN.

4. The procedure for handling NGAP messages from NG-RAN is used to route NGAP messages from NG-RAN to the AIOTF, see clause 6.2.4.3.