nding the session. 4) to 7) As described earlier, these messages are used to trigger the release of the dedicated bearer. 8), 9), 10) Bob's UA entity (or Alice's) sends the 200 OK response to the BYE request, to the domain homeA. net (or homeB net). 11) to 16) As described earlier, these messages are used to remove the dedicated bearer. P-CSCF S-CSCF SIP BYE SIP BYE SIP BYE DIAMETER STR DIAMETER RAR DIAMETER RAA DIAMETER STA SIP 200 OK GTPv2-C DELETE BEARER REQUEST SIP 200 OK GTPv2-C DELETE BEARER REQUEST SIP 200 OK ESM DEACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST S1-AP E-RAB RELEASE COMMAND RRC ConnectionReconfiguration ESM DEACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT RRC ConnectionReconfigurationComplete S1-AP E-RAB RELEASE RESPONSE GTPv2-C DELETE BEARER RESPONSE GTPv2-C DELETE BEARER RESPONSE Figure 3.8. Termination of VoLTE session: received side 3.7. Establishment of ViLTE session The procedure for establishing the ViLTE session is identical to that described for the VoLTE session when the SDP protocol associated with the initial INVITE request contains the negotiation of the two media, audio and video, with a proposal for codecs for both media. Similarly, the 183 Session Progress response defines the codec selected among the proposals, for each media. 102 VoLTE and ViLTE Upon receipt of the 183 Session Progress response, the P-CSCF entity triggers to the PCRF entity to establish two dedicated bearers: - one dedicated bearer (QCI = 1) for audio flow; - one dedicated bearer (QCI=2) for video flow. The ViLTE session can also be added to a VoLTE session. The procedure of the addition of the video stream for the ViLTE session, at the initiated side, is described in Figure 3.9. P-CSCF S-CSCF SIP UPDATE SIP UPDATE SIP UPDATE SIP 200 OK SIP 200 OK DIAMETER AAR DIAMETER RAR GTPv2-C CREATE BEARER REQUEST GTPv2-C CREATE BEARER REQUEST ESM ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST S1-AP E-RAB SETUP REQUEST RRC ConnectionReconfiguration ESM ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT RRC ConnectionReconfigurat