Policy and Charging Control (PCC) over S9 reference point; Stage 3
The present document provides the Stage 3 specification of the S9 reference point for the present release. The functional requirements of Stage 2 specification for the S9 reference point are contained in 3GPP TS 23.203 [2]. The S9 reference point lies between the PCRF in the home PLMN (also known as H-PCRF) and the PCRF in the visited PLMN (also known as V-PCRF).
Whenever it is possible the present document specifies the requirements for the protocols 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.