Question: What triggers the increment of the 'Number of background data transfer policy update requests' measurement in a 5G network, as per NEF (Network Exposure Function) interactions with AF (Application Function)?
Option 1: Successful transmission of an Nnef_ApplyPolicy_Update response message from NEF to AF.
Option 2: Receipt by the AF of a policy update request from the NEF.
Option 3: Receipt by the NEF of an Nnef_ApplyPolicy_Update request message from AF.
Option 4: A change in packet switched traffic patterns.
Explanation: This is correct because the measurement for 'Number of background data transfer policy update requests' increments upon the NEF receiving an Nnef_ApplyPolicy_Update request message from AF, highlighting the importance of signaling in telecom networks for session and policy management.