Diameter is a peer-to-peer protocol that involves delivering attribute-value pairs (AVPs). A Diameter message includes a header and one or more AVPs. The collection of AVPs in each message is determined by the type of Diameter application, and the Diameter protocol also allows for extension by adding new commands and AVPs. Diameter enables multiple peers to negotiate their capabilities with one another, and defines rules for session handling and accounting functions.

Converged Application Server includes an implementation of the base Diameter protocol that supports the core functionality and accounting features described in RFC 3588 (http://www.ietf.org/rfc/rfc3588.txt). Converged Application Server uses the base Diameter functionality to implement multiple Diameter applications, including the Sh, Rf, and Ro applications described later in this document.

You can also use the base Diameter protocol to implement additional client and server-side Diameter applications. The base Diameter API provides a simple, Servlet-like programming model that enables you to combine Diameter functionality with SIP or HTTP functionality in a converged application.

The sections that follow provide an overview of the base Diameter protocol packages, classes, and programming model used for developing client and server-side Diameter applications. See also the following sections for information about using the provided Diameter protocol applications in your SIP Servlets:

• "Using the Diameter Sh Interface Application" describes how to access and manage subscriber profile data using the Diameter Sh application.

• "Using the Diameter Rf Interface Application for Offline Charging" describes how to issue offline charging requests using the Diameter Rf application.

• "Using the Diameter Ro Interface API for Online Charging" describes how to perform online charging using the Diameter Ro application.