A mobile communication system includes a mobile communication network connected to a core network (CN) and a plurality of radio network nodes included in the mobile communication network (RAN). Network resources for a data flow between a data transmission node and a data reception node that passes through the CN and RAN are reserved on the basis of RSVP. A region for refreshing a reservation state of network resources concerning the flow is divided into a CN side and an RAN side by taking a predetermined radio network node through which the flow passes as a boundary. Refreshment on the RAN side is conducted with a frequency higher than that of refreshment on the CN side.