What triggers the AF to request the network to send an Application trigger to the UE?
The NEF invokes the Nnef_Trigger_Delivery request service.
The AF determines the need to trigger the device.
The NEF checks that the AF is authorized to send trigger requests.
The NEF invokes Nudm_SDM_Get (Identifier Translation, GPSI and AF Identifier).
The UDM may invoke the Nudr_DM_Query service to retrieve a list of AF's that are allowed to trigger the UE.