Abstract: A handover method in a mobile communication system utilizing the Mobile IP, which method solves the problem of the loss of communication packets (packet loss) and deterioration of the quality of service occurring when switching communication media, including switching connection from a first network NW1 to which a terminal is currently connected to a second network NW2 at which time transferring once to a third network NW3 (first step), establishing connection with the second network NW2 during the transfer (second step), then breaking the connection with the third network NW2 and transferring to the second network NW2 (third step).

Abstract: A QoS setup method comprises the steps of a mobile node MN recognizing a first QoS setup request when an opposite correspondent node CN makes the first QoS setup request for its route to the home address HoA of the mobile node MN, the mobile node MN making a second QoS setup request, and establishing the second QoS setup for a route between the home address HoA and Care-of Address CoA of the mobile node MN. This method makes it possible to carry out QoS setup for a section to a moved-to place of a mobile node MN in response to a QoS setup request from an opposite correspondent node CN, even if the correspondent node CN and mobile node do not have a function of route optimization.

Abstract: A handover method in a mobile communication system utilizing the Mobile IP, which method solves the problem of the loss of communication packets (packet loss) and deterioration of the quality of service occurring when switching communication media, including switching connection from a first network NW1 to which a terminal is currently connected to a second network NW2 at which time transferring once to a third network NW3 (first step), establishing connection with the second network NW2 during the transfer (second step), then breaking the connection with the third network NW2 and transferring to the second network NW2 (third step).