A conventional node 3 divides an IP packet into data fragments and prepares a packet for RAN 9 transmission. There has been a problem that, since a RAN 6 cannot identify an IP packet unit, affinity is low relative to an IP network 1 that serves as a core. A node 3 prepares A10 packets by dividing an IP packet, and adds, to each A10 packet, a concatenation flag that indicates information stored in the A10 packet is the head or the tail of the IP packet. A base station 5 and a packet control device 4 employ the concatenation flag to control transmission for each IP packet unit. For example, a packet control device 4 employs a concatenation flag to discard information for a series of A10 packets received by the node, including information that constitutes the same IP packet.