Diameter protocol is an authentication, authorisation, and accounting (AAA) protocol that serves as a replacement for the older RADIUS protocol.

It plays a crucial rule in mobile networks., as it ensures secure, controlled, and accountable access to mobile network services, as well as enabling efficient policy management, charging, and mobility support.

The key functions of the Diameter protocol include,

• It authenticates users and devices accessing the mobile network, as it provides a standard way to exchange authentication information, such as user credentials, between the network elements.

• It is responsible for authorising the services and resources that users or devices are allowed to access within the mobile network.

• Network nodes use Diameter protocol to report usage data, such as session duration, data volume, and network resources consumed, for billing and charging purposes.

• It is a key component in the policy and charging control (PCC) architecture of mobile networks, as it enables the communication between policy servers, charging systems, and other network elements to enforce policies, manage subscriber profiles, and facilitate real-time charging.