Diameter Credit-Control Application (application id: 4)

The Diameter Credit-Control Application provides a framework for implementing real-time credit control in various telecommunication services. This application is essential in environments where services are delivered to end users based on prepaid accounts or where real-time cost and credit management are required. The key functionality of the Diameter Credit-Control Application is to ensure that the user’s account has sufficient funds to cover the cost of services before they are initiated and to manage ongoing service costs in real time.

The primary purpose of the Diameter Credit-Control Application is to manage credit authorization and accounting in real-time. This ensures that services, such as network access, SIP-based services, and messaging, are only provided if the user has the necessary prepaid balance. The application is designed to work across different service environments, ensuring that credit authorization is handled consistently and efficiently.
The application interacts with the service element (such as a Network Access Server or SIP Proxy) and a Credit-Control Server (CCS) to facilitate the exchange of credit information. This exchange allows for the authorization, reservation, and deduction of credit from the user's account, ensuring that services are only provided when they are financially covered.

The architecture of the Diameter Credit-Control Application consists of the following components:

• Service Element (SE): The Service Element can be any network device or application server that provides a service to the end user. It acts as the client in the credit-control process, communicating with the Credit-Control Server.
• Credit-Control Server (CCS): The CCS is responsible for managing the credit control process, including credit authorization, reservation, and accounting. It ensures that the user's account balance is sufficient to cover the cost of the requested service.
• AAA Infrastructure: The Authentication, Authorization, and Accounting (AAA) infrastructure supports the credit-control process by ensuring that users are authenticated and authorized before services are delivered.
• Credit-Control Client (CCC): Integrated into the Service Element, the CCC is responsible for sending requests to and receiving responses from the CCS regarding the user's credit status.
• Business Support System (BSS): The BSS is typically part of the Credit-Control Server and handles billing and account management functionalities. It records transactions and ensures accurate billing for services provided.

Diameter Credit-Control Application interface workflow:

1. Service Request: When an end user requests a service (e.g., network access, SIP call), the Service Element sends a Credit-Control Request (CCR) message to the Credit-Control Server. This message includes details about the requested service and the user's account.
2. Credit Authorization: Upon receiving the CCR, the Credit-Control Server evaluates the user’s account balance to determine if sufficient funds are available. The server may reserve a portion of the user's credit for the service.
3. Credit-Control Answer (CCA): If the user's account balance is adequate, the Credit-Control Server sends a Credit-Control Answer (CCA) message back to the Service Element, authorizing the service. If the balance is insufficient, the CCA may deny the service or instruct the Service Element to provide limited access.
4. Service Delivery: Once authorized, the Service Element begins delivering the service to the user. Throughout the service, the Service Element monitors usage and may communicate with the Credit-Control Server for further authorization if additional resources are needed.
5. Service Termination: When the service is completed or the user's credit is exhausted, the Service Element informs the Credit-Control Server, which deducts the final amount from the user's account and closes the session.
6. Session Management: In session-based credit control, the session is maintained throughout the service duration, with both the Service Element and the Credit-Control Server responsible for tracking session state.

Key Features

• Money Reservation: The application supports the reservation of a specific amount of money in the user's account before service initiation, ensuring that funds are available to cover the service.
• Direct Debiting: The application allows for immediate deduction of the user's account balance upon service initiation.
• Session and Event-Based Charging: The application can handle both session-based and one-time event charges, making it versatile for different service types.
• Flexible Failure Handling: The application defines mechanisms for handling failures in communication between the Service Element and Credit-Control Server, allowing service providers to manage risks and ensure service continuity.
• Multi-Service Environment: The application supports multiple simultaneous service requests from the same user, ensuring that each service is authorized and billed independently.

For complete technical specification of Ro interface in Diameter protocol please refer to: [RFC8506]