Ro (application id: 3)

The Ro interface is specifically designed to handle real-time online charging in telecommunications networks. The Ro interface is used to facilitate communication between the Charging Trigger Function (CTF) and the Online Charging Function (OCF), allowing operators to manage charging events and credit control in real-time.

Ro interface workflow

1. Event Detection: 
   • When a chargeable event occurs, such as the initiation of a voice call or a data session, the CTF detects this event and generates a Credit-Control-Request (CCR) message. This message is then sent to the OCF via the Ro interface.
2. Credit Authorization: 
   • Upon receiving the CCR, the OCF checks the user's account balance and determines if the requested service can be authorized based on available credit. The OCF then sends a Credit-Control-Answer (CCA) message back to the CTF, indicating whether the service is allowed to proceed.
3. Service Delivery: 
   • If the service is authorized, the CTF proceeds to deliver the requested content or service. Depending on the session's progress, additional CCR messages may be sent to update the OCF or request further authorization if the user continues to consume resources.
4. Credit Deduction: 
   • The OCF deducts the appropriate amount of credit from the user’s account based on the consumed service. This process continues until the session ends or the user’s balance is exhausted.
5. Session Termination: 
   • Once the session or event is completed, the CTF sends a final CCR message to indicate session termination. The OCF responds with a CCA message, finalizing the transaction and ending the session.
6. Billing and Record-Keeping: 
   • The CGF collects all charging records generated during the session and forwards them to the Billing Domain for processing and billing. These records may also be retained for auditing and reporting purposes.

For complete technical specification of Ro interface in Diameter protocol please refer to: [3GPP TS 29.251], [3GPP TS 29.299]