 interpretation; The MRFC entity forwards the data necessary for the generation of charging tickets. Network Architecture The MFRP entity generates media flows under the control of the MRFC, such as telephone announcements. The MFRP entity combines media flows to provide a conferencing service. The MFRP entity can also perform particular treatments of the media flows, such as the transcoding of the audio signal. 1.2.2. Protocol architecture The Gm interface is the reference point between the EU and P-CSCF entities. This interface supports SIP and Session Description Protocol (SDP) signaling. The Ut interface is the reference point between the EU and TAS entities. This interface supports XML Configuration Access Protocol (XCAP) signaling, allowing the configuration of supplementary services by the mobile. The Mw interface is the reference point between the CSCF entities. This interface supports SIP and SDP signaling. The Mx interface is the reference point between, on the one hand, the CSCF entities and, the other hand, the interconnection with the Circuit- Switched (CS) network or the IMS network. This interface supports SIP and SDP signaling. The Mr interface is the reference point between the S-CSCF and MRFC entities. This interface supports SIP and SDP signaling. The Mb interface is the reference point between the UE and MRFP entities. This interface supports the RTP stream. The IMS service control (ISC) interface is the reference point between the S-CSCF and TAS entities. This interface supports SIP and SDP signaling. VoLTE and ViLTE 1.3. Databases 1.3.1. Functional architecture The HSS entity is a database storing the data specific to each user. The main data stored include the identities of the users, the authentication parameters and the service profile. The subscriber has a private identity IMSI used when attaching to the EPS network. The subscriber has an IMS private identity (IMPI) used while registering to the IMS network, and an IMS public identity (IMPU) when establishing a voice or a conversational 