00 Trying DIAMETER LIR DIAMETER LIA SIP INVITE (SDP Réseau CS) SIP 100 Trying SIP 183 Session in Progress SIP 183 (SDP Bob) Session in Progress SIP 183 (SDP Bob) Session in Progress (SDP Bob) SIP PRACK SIP PRACK SIP 200 OK SIP 200 OK SIP UPDATE (SDP Réseau CS) SIP UPDATE (SDP Réseau CS) SIP 200 OK (SDP Bob) SIP 200 OK SIP 180 Ringing (SDP Bob) SIP 180 Ringing SIP 180 Ringing SIP 200 OK (ISUP ACM) SIP 200 OK SIP 200 OK (ISUP ANM) SIP ACK SIP ACK Figure 6.8. Session establishment initiated by CS network SIP-I signaling 11) The provisional response 183 Session in Progress to the INVITE request is extended to the CS network. 12) The PRACK request is generated by the CS network. 15) The 200 OK response to the PRACK request is extended to the CS network. VoLTE and ViLTE 16) The UPDATE request is generated by the CS network. 19) The 200 OK response to the UPDATE request is extended to the CS network. 22) The ISUP ACM message is transmitted in the provisional response 180 Ringing to the INVITE request. 25) The ISUP ANM message is transmitted in the 200 OK response to the INVITE request. 26) The ACK request is generated by the CS network. 6.1.4. Session termination 6.1.4.1. Session termination initiated by IMS network Procedure for the release of the session initiated by the IMS network is displayed in Figure 6.9. S-CSCF network SIP BYE SIP BYE ISUP/BICC REL SIP BYE (ISUP REL) ISUP / BICC RLC SIP 200 OK (ISUP RLC) SIP 200 OK SIP 200 OK Figure 6.9. Session clearing initiated by IMS network ISUP, BICC or SIP-I signaling 1), 2) The UA entity terminates the communication by generating the BYE request. 3) Upon receipt of the BYE request, the MGCF entity removes the end- points of the IMS-MGW gateway and generates the message ISUP/BICC REL to the CS network, in the case of ISUP/BICC signaling. In the case of SIP-I signaling, the ISUP REL message is carried in the BYE request. Interconnections 4) In the case of ISUP/BICC signaling, the CS network responds with the message ISUP / BICC RLC. In the case of SIP-I signaling, the ISUP