 respectively PGW entity) responds to the MME entity (or respectively SGW entity) with the CREATE SESSION RESPONSE message. The signaling bearer is deactivated by the exchange of the DELETE SESSION REQUEST/RESPONSE messages. The procedure is triggered when the mobile detaches, when the traffic is released, when the TAC changes, leading to a modification of the SGW entity, or when handover occurs, with a switch of the SGW. The dedicated bearer specific to a mobile is created similarly, modified possibly and deleted by the exchange of the following messages: - CREATE / MODIFY / DELETE BEARER REQUEST; - CREATE / MODIFY / DELETE BEARER RESPONSE. The DOWNLINK DATA NOTIFICATION message is sent by the SGW entity to the MME entity, over the S11 interface. The procedure follows the reception by the SGW entity of data from the PGW entity, with the mobile in ECM-IDLE mode. Just after receiving this message, the MME entity sends the S1-AP PAGING message to the eNB entities belonging to the TAC. VoLTE and ViLTE The MME entity may respond with the DOWNLINK DATA NOTIFICATION ACKNOWLEDGE message, indicating whether or not the request is accepted or with the DOWNLINK DATA NOTIFICATION FAILURE INDICATION message if the mobile does not respond to the paging or if the mobile service request is rejected. The CREATE INDIRECT DATA FORWARDING TUNNEL REQUEST/RESPONSE messages create a specific traffic bearer when handover occurs. This bearer forwards the data traffic received by the source eNB entity to the SGW entity to then be re-transmitted to the mobile via the target eNB entity. 2.5.2. Mobility management Mobility management messages are exchanged between the source and target MME entities, when the handover of the mobile imposes a switch of MME entity. The source MME entity sends the target MME entity the FORWARD RELOCATION REQUEST message containing the context of the mobile. The target MME entity responds with the FORWARD RELOCATION RESPONSE message when the resources needed for the handover have been reserved. The response conta