Question: In the context of the Rx interface for Policy and Charging Control, what is the role of the PCRF (Policy and Charging Rules Function) in relation to the Diameter protocol?
Option 1: The PCRF acts as a Diameter client, requesting authorization of resources for an AF session.
Option 2: The PCRF acts as a Diameter server, handling AF session authorization requests for a particular realm.
Option 3: The PCRF operates as both a Diameter client and server, depending on the application identification AVP.
Option 4: The PCRF does not interact with the Diameter protocol directly; it only communicates via the Gq interface.
Explanation: According to Policy and Charging Control specifications for the Rx interface, the PCRF handles AF session authorization requests, positioning it as a Diameter server. This contrasts with the Application Function (AF), which acts as the Diameter client initiating these requests. Thus, the PCRF's correct role is that of a server.