ibed in Figure 1.10. The PCRF entity provides to the PCEF entity, integrated in the PGW entity, the necessary information for the control and the charging of the traffic data (IP packets). This information is stored in the subscription profile repository (SPR) during the creation of the subscription. Traffic control includes the following: - association between a service data flow (SDF) and EPS bearer; - blocking or allowing IP packets; - allocation of QCI parameter to EPS bearer. VoLTE and ViLTE IMS (P-CSCF) Figure 1.10. Functional architecture of PCC The charging method defines as if the PCEF entity has to obtain credit from the OCS entity for online charging or if it has to generate information submitted to the OFCS entity. The PCEF entity executes the rules provided by the PCRF entity to control the traffic flow, the accounting of traffic volume and the charging. The PCEF entity may relate to the PCRF entity a change of state of a service flow, as in the case of loss of radio coverage of the mobile. The PCRF entity may receive a session request from the AF (Application Function) entity as in the case of the establishment of a voice or conversational video communication initialized at the IMS network. The PCRF entity may provide the AF entity information about events occurring in the mobile network as in the case of loss of radio coverage of the mobile. In case of roaming, PCEF entity located in the visited network requests rules to the Visited-PCRF (V-PCRF) entity, which gets them from the Home-PCRF (H-PCRF) entity. 1.5.2. Protocol architecture The Gx interface is the reference point between the PCRF and PCEF entities. This interface supports the DIAMETER signaling. Network Architecture The Rx interface is the reference point between the PCRF entity and the AF entity, represented by the P-CSCF entity as in the case of the IMS network. This interface supports the DIAMETER signaling. The Gy interface is the reference point between the PCEF and OCS entities. This interface supports the DIAMETER signaling. The Gz