In ZigBee, there are three different types of devices: end device, router, and coordinator. The key difference between these is that an end device can not route traffic, routers can route traffic, and the coordinator, in addition to routing traffic, is responsible for forming the network in the first place. Every network must have one and only one coordinator. These differences dictate the different features of each type of device.
Any platform, EM250, EM260, and EM2420 can act like an end device, router, or coordinator. Ember provides one stack for each of these platforms. This stack is capable of operating as an end device, a router, or a coordinator.
Here is a more detailed description of the capabilities of each device type:
End Device: End devices do not route traffic. In EmberZNet, end devices may be mobile devices. They may also sleep, which makes end devices a suitable choice for battery operated devices. Because end devices may sleep, all traffic to an end device is first routed to its parent. The end device is responsible for requesting any pending messages from its parent. If an end device has moved, it is responsible for informing the network that it has rejoined to a new parent.
Router: Routers are responsible for routing traffic between different nodes. In EmberZNet 3.0, routers may not sleep. As such, routers are not a suitable choice for battery operated devices. Routers are also responsible for receiving and storing messages intended for their children. In addition to this, routers are the gate keepers to the network. They are responsible for allowing new nodes to join the network.
Coordinator: A coordinator is a special router. In addition to all of the router capabilities, the coordinator is responsible for forming the network. To do that, it must select the appropriate channel, PAN ID, and extended network address. It is also responsible for selecting the security mode of the network. In a network that is using standand security in Zigbee2007, the coordinator will be used as the trust center for the network. The trust center is responsible
for authenticating new nodes & distributing network keys to new nodes as they join the network.