A network system, a network control method, and a control apparatus are provided that can easily achieve assurance of the quality of a network service and optimization of the throughput of an entire system. A network control apparatus (10) controls a network (20) having a multi-layer structure, monitors whether or not a network service on a first layer fulfills a required service level, and depending on a result of the monitoring, changes a setting of a packet header so that resources on the first layer will be changed, wherein resources on the lower layer are changed in accordance with a change in the setting of the packet header.