scope:

The present document provides the stage 3 specification of the Gx, Gxx and Sd reference points for the present release. The present document also provides the Diameter variant of St reference point for the present release. The functional requirements and the stage 2 specifications of the Gx, Gxx, Sd and St reference points are contained in 3GPP TS 23.203 [7]. The Gx reference point lies between the Policy and Charging Rule Function and the Policy and Charging Enforcement Function. The Gxx reference point lies between the Policy and Charging Rule Function and the Bearer Binding and Event Reporting Function. The Sd reference point lies between the Policy and Charging Rule Function and the Traffic Detection Function. The St reference point lies between the Policy and Charging Rule Function and the Traffic Steering Support Function.

Whenever it is possible the present document specifies the requirements for the protocol by reference to specifications produced by the IETF within the scope of Diameter. Where this is not possible, extensions to Diameter are defined within the present document.