g the message EMM DETACH REQUEST. Signaling Protocols The response EMM DETACH ACCEPT concludes the detachment procedure. The response is not transmitted by the MME entity if the detach request sent by the mobile indicates that it has been turned off. The detachment procedure implicitly causes the release of the active bearers. 2.1.1.2. Authentication The procedure of mutual authentication is initiated by the MME entity by sending the message EMM AUTHENTICATION REQUEST, containing a random number RAND and the authentication network (AUTN). The mobile uses the RAND received to locally compute its own authentication code RES (Result) and that of the network (AUTN) and compares the AUTN calculated to the one received from the MME entity. If the MME entity is authenticated, the mobile responds with the message EMM AUTHENTICATION RESPONSE, containing the authentication code RES. Otherwise, it indicates that network authentication failed with the message EMM AUTHENTICATION FAILURE. The MME entity compares the RES value received from the mobile with that communicated by the HSS. If the two codes are the same, the mobile is authenticated and the MME entity triggers security mode for NAS signaling. Otherwise, the MME entity responds with the message EMM AUTHENTICATION REJECT. 2.1.1.3. Security mode When mutual authentication has been successful, the MME begins putting the NAS signaling in security mode by sending the message EMM SECURITY MODE COMMAND. The integrity of this message is protected. If the check on the integrity of the message EMM SECURITY MODE COMMAND is positive, the mobile responds with the message EMM SECURITY MODE COMPLETE. All subsequent NAS messages are then encrypted and their integrity is checked. VoLTE and ViLTE If the check on the integrity of the message EMM SECURITY MODE COMMAND is negative, the mobile responds with the message EMM SECURITY MODE REJECT. 2.1.1.4. Tracking area update The procedure of tracking area update is periodically initiated SO that the mobile can maintain its tracking area or 