Question: In a 3GPP Northbound API architecture with cascaded API Exposing Functions (AEFs), what is the primary role of the first AEF instance in relation to service API invocations?
Option 1: To provide the functionality of the actual service APIs directly to User Equipment (UE).
Option 2: To act solely as a load balancer for distributing API requests across multiple AEF instances.
Option 3: To handle all billing and charging functions related to service API usage.
Option 4: To serve as an access controller, providing entry point for the service API and enforcing access control.
Explanation: In the context of cascaded AEFs in a 3GPP Northbound API framework, the first AEF instance is crucial for controlling access to the service APIs. It acts as the entry point, ensuring that only authorized entities can invoke the service APIs, thereby protecting the network and services from unauthorized access.