Push-Notification-Answer (PNA) Table 2.17. DIAMETER messages over Sh interface VoLTE and ViLTE UDR and UDA messages allow the TAS entity to retrieve profile data stored in the HSS entity. PUR and PUA messages allow the TAS entity to update the profile data stored in the HSS entity. SNR and SNA messages allow the TAS entity to subscribe to notifications relating to modifications of profile data stored in the HSS entity. PNR and PNA messages allow the TAS entity to receive the notification of modifications in the profile data stored in the HSS entity. 2.8.3. Application to PCC function Table 2.18 summarizes DIAMETER messages exchanged over the Gx interface between policy charging and rules function (PCRF) and policy and charging enforcement function (PCEF) hosted in the PGW entity. Request Response Credit-Control-Request (CCR) Credit-Control-Answer (CCA) Re-Auth-Request (RAR) Re-Auth-Answer (RAA) Table 2.18. DIAMETER messages over Gx interface CCR and CCA messages enable the PCEF entity to solicit the PCRF to: - retrieve the rules to apply to the default bearer created by the EPS network; - inform the PCRF entity to the termination of the session on the EPS network. RAR and RAA messages allow the PCRF entity to solicit the PCEF entity in order to provide the rules to be applied for the dedicated bearer. Signaling Protocols Table 2.19 summarizes DIAMETER messages exchanged over the Rx interface between the PCRF and AF (Application Function) entities. Request Response Authenticate and Authorize Request (AAR) Authenticate and Authorize Answer (AAA) Re-Auth-Request (RAR) Re-Auth-Answer (RAA) Session Termination Request (STR) Session Termination Answer (STA) Abort-Session-Request (ASR) Abort-Session-Answer (ASA) Table 2.19. DIAMETER messages over Rx interface AAR and AAA messages allow the AF entity to provide the characteristics of the media SO that the EPS network can establish the dedicated bearer. RAR and RAA messages allow the PCRF entity to notify the AF entity that a number of IP flows were disabled following a d