When a radio terminal unit 30 undergoes a handover between base stations 34, 36, a previous edge router 40 having been connected to the radio terminal unit 30, out of edge routers 40, 42 provided in respective base stations 34, 36, provides an instruction to instruct a relay router 48, under which the edge router 40 and every edge router 42 in the base station 36 as a candidate for a destination of the movement are connected, to buffer data from a correspondent node, and instructs the relay router to forward the data buffered in the relay router 48 according to the instruction, to the radio terminal unit 30 after the movement, after completion of the handover, whereby the buffered data is forwarded to the radio terminal unit 30. This implements forwarding packet data through the optimal path to the radio terminal unit after the movement in the handover control and achieves effective utilization of network resources and reduction of handover transactions.