 200 SIP 200 Clearing of the session established between Alice and Bob Transfer of the session established between Alice and Carol to the conference bridge Audio flow Clearing of the session established between Alice and Carol Figure 5.8. CONF 164 VoLTE and ViLTE The MRFC entity sends a NOTIFY request to Alice's UA entity to indicate that the transfer has been activated. The header Subscription- State assumes the value active. The MRFC entity initializes an INVITE request to Bob's UA entity, using the parameters communicated in the REFER request in the header Replaces. The session is established between Bob's UA entity and the conference bridge. The MRFC entity sends a NOTIFY request to Alice's UA entity to communicate that the transfer has been terminated. The header Subscription-State assumes the value terminated. Alice's UA entity sends a BYE request to Bob's UA entity to release the previously-established session. 5.2.1.6. Communication waiting Communication waiting (CW) gives information to the caller telling them that the callee is on a different communication but that he has been notified of the call. Two possible scenarios may occur: - if the telephony application server knows the callee's status and if the service is activated (case 1), it inserts the communication waiting indication into the INVITE request sent to the callee; - otherwise (case 2), the TAS entity is informed of the situation in the response given by the callee. The different exchanges relating to communication waiting, for case 1, are shown in Figure 5.9. 1), 2), The INVITE request containing the SDP message of the caller is transferred to Bob's TAS entity. 3), 4), 5) The telephony application server adds a second XML message (application/vnd. 3gpp. CW+xml) giving the communication waiting indication, to the message body containing an SDP message (application/sdp) in the INVITE request, received from the S-CSCF entity. Service Profiles The telephony application server indicates in the header Content- Type that multiple messages appear in