eactivation applied at the PCEF entity. STR and STA messages allow the AF entity to inform the session is finished, SO that the EPS network releases the bearer dedicated. ASR and ASA messages allow the PCRF entity to notify the AF entity that session on the EPS network is complete, for example as a result of the loss of coverage of the mobile. DIAMETER messages exchanged over R9 interface between home PCRF (H-PCRF) and visited PCRF (V-PCRF) are identical to the messages exchanged over Gx and Rx interfaces. Table 2.20 summarizes DIAMETER messages exchanged over the Gz interface between the PCEF entity and offline charging system (OFCS). VoLTE and ViLTE The same DIAMETER messages are exchanged over the Rf interface between, on the one hand, the entities of the IMS network, and, on the other hand, the OFCS entity. Request Response Accounting-Request (ACR) Accounting-Answer (ACA) Table 2.20. DIAMETER messages over Gz interface ACR and ACA messages enable the PCEF entity to inform the OFCS entity periodically on the consumption of resources in the case of post-paid service. Table 2.21 summarizes DIAMETER messages exchanged over Gy interface between the PCEF entity and online charging system (OCS). Request Response Credit-Control-Request (CCR) Credit-Control-Answer (CCA) Re-Auth-Request (RAR) Re-Auth-Answer (RAA) Abort-Session-Request (ASR) Abort-Session-Answer (ASA) Table 2.21. DIAMETER messages over Gy interface The same DIAMETER messages are exchanged over the Ro interface between, on the one hand, media gateway control function (MGCF), IMS- GWF (gateway function) and TAS entities of the IMS network, and, on the other hand, the OCS entity. CCR and CCA messages enable the PCEF entity to recover credit from OCS entity in the case of pre-paid service. Signaling Protocols RAR and RAA messages allow the OCS entity to initialize a new authentication or new authorization. ASR and ASA messages allow the OCS entity to end the current DIAMETER session. Basic Procedures 3.1. Attachment At the end of the connection procedure, t