In order to make it possible to report an amount of data from a secondary node (SN) to a master node (MN) in dual connectivity, there is provided a first unit according to the present disclosure which is a first unit of a central unit of a first base station. The first unit includes a controller and a transceiver. The central unit is configured to host at least PDCP layer in the first base station; and is connected to a distributed unit via a first interface, the distributed unit hosting RLC, MAC and PHY layers in the first base station. The controller is configured to host at least a user plane of the PDCP layer hosted by the central unit; and the transceiver is configured to transmit, to a second unit via a second interface, first information indicative of a volume of data processed by the first unit. The second unit is configured to host at least a control plane of the PDCP layer hosted by the central unit.