A network system which provides each terminal user with differentiated service, dynamically changing service profiles even in the middle of a communication session. A service control database maintains service profile definitions. When a mobile node registers with a foreign agent to initiate a conmiunication session, a service profile setting controller in the mobile node's home server sets up a service profile for the mobile user. When an event occurs within a service profile updating controller, it indicates that some control condition specified in the service profile is met. The service profile updating controller then makes access to the service control database to obtain a new service profile and the mobile node's foreign server forwards it to the foreign agent, to which the mobile node is attached. The service profile that has been established in relevant network nodes, including the home agent and foreign agent, is dynamically updated with the new one.