The message between the network nodes may be a request for addition, modification, or release in the secondary node, and the predetermined condition may be that the field does not include a data type in which setup or release is specified. With this configuration, in a case where the data type “SetupRelease” is not used, the base station apparatus 10 can perform configuration by assuming that all fields related to functions configured in the user apparatus 20 are mandatory.
In a case where the field includes a data type in which setup or release is specified, the field may be capable of a delta configuration. With this configuration, in a case where the data type “SetupRelease” is used, the base station apparatus 10 can perform a delta configuration for the functions configured in the user apparatus 20.
(Supplement of Embodiment)