A network system including a plurality of devices can acquire authenticated location information of a device and provides various services using the authenticated location information. Each of the plurality of devices includes: a communication unit for performing data communication with another device; a storage unit that stores a digital certificate including a public key for determining an IP address of the device; and a determination unit that determines an IP address of another device based on a public key included in a digital certificate received from the another device. The digital certificate includes location information associated with a corresponding device.