A method, by a service control entity (100, 300), to set up a communication path for exchange of service control messages with a service application entity in a mobile communications network for controlling an application of a service, by the service application entity, to a media data flow, the media data flow being established between the service control entity (100, 300) and a remote end, the method comprising the steps of: - transmitting a first message on a service control channel, the first message comprising as a destination address an address of the remote end, wherein offer data is added to the transmitted first message, the offer data including an indicator indicating that the service control entity is configured to support a communication path on a media data plane of the media data flow based on Real Time Transport Control Protocol, RTCP, service control messages, - receiving a second message on the service control channel, wherein the second message comprises acceptance data in response to the offer data, the acceptance data comprising a receiver address at which the service application entity is configured to receive RTCP service control messages, - storing the receiver address at which the service application entity is configured to receive RTCP service control messages in order to set up the communication path between the service control entity and the service application entity, - receiving an encryption key of the service application entity via the service control channel, - storing the encryption key of the service application entity at the service control entity (100, 300), - generating a control command for the service application entity, comprising as a destination address an address of the remote end, - encrypting the control command using the stored encryption key from the service application entity, - transmitting the encrypted control command on the media data plane in direction of the service application entity. - transmitting a first message on a service control channel, the first message comprising as a destination address an address of the remote end, wherein offer data is added to the transmitted first message, the offer data including an indicator indicating that the service control entity is configured to support a communication path on a media data plane of the media data flow based on Real Time Transport Control Protocol, RTCP, service control messages, - receiving a second message on the service control channel, wherein the second message comprises acceptance data in response to the offer data, the acceptance data comprising a receiver address at which the service application entity is configured to receive RTCP service control messages, - storing the receiver address at which the service application entity is configured to receive RTCP service control messages in order to set up the communication path between the service control entity and the service application entity, - receiving an encryption key of the service application entity via the service control channel, - storing the encryption key of the service application entity at the service control entity (100, 300), - generating a control command for the service application entity, comprising as a destination address an address of the remote end, - encrypting the control command using the stored encryption key from the service application entity, - transmitting the encrypted control command on the media data plane in direction of the service application entity.