Further, each of the base station apparatus 10 and the user apparatus 20 may include hardware such as a micro processor, a digital signal processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), a FPGA (Field Programmable Gate Array), etc., and a part or all of each functional block may be realized by the hardware. For example, the processor 1001 may be implemented by at least one of the above hardware elements.

(Embodiment Summary)

As described above, according to an embodiment of the present invention, provided is a network node including: a control unit configured to configure an information element in a field included in a message between network nodes in a case where the field is mandatory in the message between the network nodes, the message being used for performing a communication configuration related to a user apparatus; and a transmission unit configured to transmit the message between the network nodes including the field in which the information element is configured, wherein the field is mandatory in a case where a predetermined condition is satisfied.