An apparatus of a first base station in a communication system, the apparatus comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive from a multi-node controller data packets to be transmitted to a user terminal; maintain one or more transmit buffers for transmitting the data packets to the user terminal; transmit the data packets to the user terminal; receive information from the user terminal regarding whether one or more of the data packets are successfully or not successfully received; transmit, to a second base station or to the multi-node controller, acknowledgement information, on the basis of the received information; characterised by further causing the apparatus to: receive a notification, from the second base station or from the multi-node controller, that one or more data packets have been successfully transmitted to the user terminal from the second base station; and if the one or more transmit buffers comprise the successfully transmitted data packets, remove these data packets from the one or more transmit buffers. at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive from a multi-node controller data packets to be transmitted to a user terminal; maintain one or more transmit buffers for transmitting the data packets to the user terminal; transmit the data packets to the user terminal; receive information from the user terminal regarding whether one or more of the data packets are successfully or not successfully received; transmit, to a second base station or to the multi-node controller, acknowledgement information, on the basis of the received information; characterised by further causing the apparatus to: receive a notification, from the second base station or from the multi-node controller, that one or more data packets have been successfully transmitted to the user terminal from the second base station; and if the one or more transmit buffers comprise the successfully transmitted data packets, remove these data packets from the one or more transmit buffers. receive from a multi-node controller data packets to be transmitted to a user terminal; maintain one or more transmit buffers for transmitting the data packets to the user terminal; transmit the data packets to the user terminal; receive information from the user terminal regarding whether one or more of the data packets are successfully or not successfully received; transmit, to a second base station or to the multi-node controller, acknowledgement information, on the basis of the received information; characterised by further causing the apparatus to: receive a notification, from the second base station or from the multi-node controller, that one or more data packets have been successfully transmitted to the user terminal from the second base station; and if the one or more transmit buffers comprise the successfully transmitted data packets, remove these data packets from the one or more transmit buffers. receive a notification, from the second base station or from the multi-node controller, that one or more data packets have been successfully transmitted to the user terminal from the second base station; and if the one or more transmit buffers comprise the successfully transmitted data packets, remove these data packets from the one or more transmit buffers.