ZigBee networks always have a single coordinator device. This device starts the network, selecting the channel and PAN ID. The coordinator is responsible for handing out addresses, allowing routers and end devices to join the network, as well as assisting in routing data. The coordinator can buffer wireless data packets for sleeping end device children. However, it cannot sleep; the coordinator must be powered ON all the time. Finally, the coordinator manages the other functions that define the network, secure it, and keep it healthy.