A packet structure and a packet transmission method of a network control protocol. A user in the inside or outside of the house can effectively control various home appliances such as refrigerator or laundry machine or monitor operation state of the devices, over the living network such as RS-485 network, low-power RF network, and power line network so that the user can enjoy the remote control and the convenient monitoring. In addition, the packet structure for the inter-layer interface of the network control protocol can be managed. The packet structure at the application layer is generated by assigning one of an application layer protocol data unit header, a request message, a response message, and an event message, together with an application layer protocol data unit header The generated packet at the application layer is transmitted to thus interface layers of the network control protocol. Therefore, the packet structure at the application layer can be more efficiently managed and transmitted.