Accounting

Accounting support and accounting messages are defined as part of the base protocol.

The accounting protocol is based on a server directed model that supports real-time delivery of accounting information. The server directed model means that the Diameter client generating the accounting data receives direction from the (authorization or accounting) server regarding accounting record timeliness requirements.

Batch accounting is not a requirement and is currently not supported by Diameter.

CMS security may be applied to Diameter accounting messages, providing strong authentication and integrity protection for accounting data.

The base protocol defines some AVPs that must be present in accounting request messages, such as the Session-Id AVP and the User-Name AVP. Each Diameter application (e.g. NASREQ, Mobile IPv4), additionally defines application-specific AVPs required in the Accounting-Request.

The Session-Id AVP can be used to correlate multiple accounting messages for a user session. Additionally, for applications that require multiple accounting sub-sessions, an Accounting-Sub-Session-Id AVP has been defined. Furthermore, for applications where a user receives service from different access devices (each with distinct Session-Ids), such as Mobile IPv4, the Accounting-Multi-Session-Id AVP, carried over from RADIUS, can be used for correlation.