Question: In the context of interaction between 5G System (5GS) QoS and session signalling, as per 3GPP specifications, what is the equivalent component(s) for the Policy and Charging Enforcement Function (PCEF) in a 5GS architecture?
Option 1: Serving and Packet Data Network Gateway (S-GW/P-GW)
Option 2: Access and Mobility Management Function (AMF)
Option 3: Session Management Function (SMF) alone
Option 4: Combination of Session Management Function (SMF) and User Plane Function (UPF)
Explanation: In the 5G System architecture, the Policy and Charging Enforcement Function (PCEF) functionalities are distributed. The combination of the Session Management Function (SMF), handling control plane policy enforcement, and the User Plane Function (UPF), handling user plane aspects including traffic steering and forwarding, together fulfill the PCEF role in enforcing QoS policies and charging rules in a 5GS environment.