Question: How is a Diameter session on the St reference point typically established between a Policy and Charging Rules Function (PCRF) and a TSSF, according to 3GPP specifications?
Option 1: The TSSF initiates the session with a Session-Initiation-Request, including the Request-Type AVP set to "2 (re-authentication request)".
Option 2: The PCRF initiates the session with a TDF-Session-Request, including the Request-Type AVP set to "0 (initial request)".
Option 3: Both PCRF and TSSF simultaneously send Capabilities-Exchange-Requests to establish the session.
Option 4: The session is established automatically upon successful transport connection without any explicit request.
Explanation: According to the specifications, the establishment of a Diameter session on the St reference point is initiated by the PCRF. This is done through a TDF-Session-Request command that includes a Request-Type AVP set to "0 (initial request)", signaling the start of a new session. This process highlights how sessions are managed in telecom networks, particularly in the context of policy and charging control, ensuring coordinated communication between network elements like PCRF and TSSF.