There are three types of devices defined in the IEEE 802.15.4 specification: the full function device (FFD), the personal area network coordinator (PAN or PANC), and the reduced function device (RFD). The FFD supports all features specified by the standard and is ideal for the network router function. It may also be used in network edge devices where the network touches the real world and gathers or sends data. The PAN or PANC is a special case FFD that establishes the network, including assigning ID and address blocks. The coordinator’s primary function is to establish the network. Once the network is formed, it takes on the role of a router. All routers or FFDs maintain association and routing information. This is the most sophisticated of the three devices and thus has the most memory or computing power. The RFD carries limited functionality, as specified by the standard, to control the cost and complexity of the device. The typical usage of the RFD is a network edge device.