se (REL) message is sent to release the resources when a user hangs up the telephone. 176 VoLTE and ViLTE Release complete (RLC) message is transmitted to acknowledge the REL message. 6.1.2.2. BICC signaling The BICC protocol is used for signaling exchanged between, on one hand, the MGCF entity of the IMS network, and, on the other hand, the entity of the CS network responsible for interconnection of the telephone signaling. The BICC protocol was developed from the ISUP protocol that it is similar for basic call procedures and functions of supplementary telephone services basically. The BICC protocol also implements a mechanism which allows for the exchange of information linked to the support command of the media flow on the IP network between, on one hand, the IMS-MGW interconnection gateway, and, on the other hand, the entity of the CS network responsible for interconnection of the media flow. This information concerns IP addresses, UDP port numbers, types of media (voice, video and data) and formats used for this media (codecs for voice and video protocols for data). This information is tunneled in BICC messages containing signaling such as for example the IAM message for communication establishment or in the BICC APM (Application Transport Mechanism) message which does not transport any signaling information. The IP bearer control protocol (IP BCP) protocol is a control protocol for media flow which aims to ensure the exchange of necessary information to establish or modify media flow characteristics. The IPBCP protocol is initialized by the IMS-MGW and passed to the MGCF entity thanks to the H.248 protocol, for which a specific package is defined. The package defines additional properties which can appear in the terminations and contexts. The IPBCP protocol defines four types of message: - REQUEST message is sent by the MGCF entity to launch a request to establish or modify a media flow on the IP network; Interconnections - ACCEPTED message is sent by the MGCF entity which receives a message of media flow e