In-vehicle network system and control method

An in-vehicle network system comprising:

• a plurality of control devices connected to a communication bus and configured to communicate with each other in a vehicle,
• wherein:
• the plurality of control devices includes at least one upper control device and a plurality of lower control devices;
• the at least one upper control device includes at least one of (i) a circuit and (ii) a processor with a memory storing computer program code executable by the processor, the at least one of the circuit and the processor configured to cause the upper control device to implement
• a power management unit configured to turn on and off a plurality of relay circuits provided in a power supply line of each of the plurality of the lower control devices,
• a startup management unit configured to receive a network management message on behalf of a plurality of the lower control devices, wherein the network management message is transmitted via the communication bus and selectively instructs a startup of the plurality of the lower control devices, to instruct the power management unit to turn on the relay circuit provided in the power supply line of the lower control device for which startup is instructed by the network management message, and to set the lower control device for which the startup is instructed to be in a startup state, and
• an abnormality location determination unit configured to detect a power supply state to the lower control devices and a communication state with the lower control devices and to determine an abnormality occurrence location based on a detection result.