diagram illustrating an uplink user data transfer performed by the radio network controller rnc and the sgsn the radio network controller rnc has ms management table 24 in which an ip address of the mobile station ms the location of which has been registered processing procedure p 10 the radio network controller rnc searches the above mentioned ms management table 24 managed by the radio network controller rnc of interest to check whether the destination of the user data having been received from a certain mobile station ms is a mobile station ms subordinate to the radio network controller rnc of interest processing procedure p 11 1 through this search it is determined whether the user data from the mobile station ms 1 is addressed to another mobile station ms subordinate to the radio network controller rnc of interest processing procedures p 12 1 12 2 if the destination is the different mobile station ms subordinate to the radio network controller rnc the user data is transferred to the mobile station ms concerned processing procedure p 13 1 otherwise the user data is transferred to the sgsn which is the superordinate node processing procedure p 13 2 according to the embodiment shown in fig1 the radio network controller rnc receives the user data from the mobile station ms 1 because the destination ip address of the user data is b which is not listed in the own ms management table 41 the radio network controller rnc determines that the destination ms is not located subordinate to the radio network controller rnc concerned accordingly the radio network controller rnc transfers the user data to the sgsn further in fig1 when the sgsn receives the user data from the radio network controller.