Mobile communication system, sgw, incoming method for a mobile communication system, and sgw how incoming

Mobile communication system according to the present invention includes a UE (45), and MME (25), and SGSN (27), and a SGW (15). A UE (45), and MME (25), SGSN (27), in the SGW (15), if the ISR is enabled, SGW (15) is, MME (25) and Downlink the SGSN (27) Data Notification send a message, MME (25) and SGSN (27) different from the other from the MME (35) or from another SGSN (37) Modify Bearer Request when receiving the message, the other that has transmitted the Modify Bearer Request message It means for retransmitting the Downlink Data Notification MME (35) or other SGSN (37) to only those with a.