 been established at this stage. It will remain blocked by the PGW entity until Bob picks up the call. 17) The PGW entity responds to the PCRF entity with the DIAMETER RAA (Re-Auth Answer) message. 18) The PCRF entity responds to the P-CSCF entity with the DIAMETER AAA (Authenticate-Authorize-Answer) message. 19) The P-CSCF entity forwards the 183 Session Progress response to the Alice's UA entity. 20), 21), 22) Alice's entity sends the subsequent PRACK request to acknowledge the provisional response 183 Session Progress. Alice's UA entity indicates in the Route headers the identities of CSCF entities processing the request, namely P / C-CSCF entities in the domains (homeA. net) and (homeB.net). 23), 24), 25) The 200 OK Message is the response to the PRACK request. 26), 27), 28) When Alice's UA entity has confirmation of the resource reservation, it indicates this to Bob's UA entity in an SDP offer (a=curr:qos local sendrecv) contained in an UPDATE request. a=curr:qos local sendrecv a=curr:qos remote none a=des:qos mandatory local sendrecv a=des: gos mandatory remote sendrecv 29), 30), 31) When Bob's UA entity has confirmation of the resource reservation, it notifies Alice's UA entity in an SDP offer contained in the response 200 OK to the UPDATE request. a=curr:qos local sendrecv a=curr:qos remote sendrecv a=des:gos mandatory local sendrecv a=des:qos mandatory remote sendrecv VoLTE and ViLTE 32), 33), 34) When the resource reservations are effective at both ends, Bob's telephone can ring and a response 180 Ringing is transmitted to Alice's UA entity, generating a ring back tone for her. 35), 36) When Bob picks up the phone, the 200 OK response to the INVITE request is sent to the PCSCF entity. 37) The P-CSCF entity sends to the PCRF entity the DIAMETER AAR message to indicate that Bob took the call. 38) The PCRF entity transmits to the PGW entity the RAR DIAMETER message to unblock the dedicated bearer. 39) The PGW entity responds to the PCRF entity with the DIAMETER AAR message. 40) The PCRF entity responds to 