Network Node Types#

The Zigbee specification supports at most one coordinator, multiple routers, and multiple end devices within a single network. These node types are described in the following sections.

Coordinator#

A Zigbee coordinator (ZC) is responsible for forming a centralized network. A coordinator is a router with some additional functionality and uses a hardcoded network address of 0x0000. Zigbee coordinator functions include selecting an appropriate channel after scanning available channels, and selecting an extended PAN ID (see Extended PAN IDs for more information about extended PAN IDs). After forming the network, the coordinator acts as a router.

The coordinator also has added responsibilities, such as being the trust center or network manager. The trust center manages the security settings and authorizations for the network. The network manager monitors and corrects network issues such as PAN ID conflicts or channel changing due to interference. These choices are up to the application developer, and in some cases are made by an application layer, such as Zigbee 3.0, being used.

Note: Only a network coordinator can be designated as a centralized trust center for security purposes when starting a network.

Routers#

Zigbee router devices provide routing services to network devices. Routers can also serve as end devices. Unlike end devices, routers are not designed to sleep and should generally remain on as long as a network is established.

End Devices#

Zigbee end devices (ZED) are leaf nodes. They communicate only through their parent nodes and, unlike router devices, cannot relay messages intended for other nodes.

Depending on the network stack, end devices can be of several types:

  • Sleepy end devices (EmberNodeType EMBER_SLEEPY_END_DEVICE) power down their radio when idle, and thus conserve resources. However, they must poll their parent node to receive incoming messages and acknowledgments; no data is sent to the sleepy end device until the end device requests it. Sleepy end devices are also sometimes known as rx-off-when-idle devices. This is a standard Zigbee device type.

  • Non-sleepy end devices (EmberNodeType EMBER_END_DEVICE) do not route messages for other devices but they remain powered during operation. These devices are known as Rx-on-when-idle devices. This is a standard Zigbee device type.

The EmberZNet PRO stack supports sleepy and non-sleepy end devices. The choice of node type must also be considered carefully. For example, in a very dense network, it is not always advantageous for all line powered nodes to be routers due to possible interference issues which may occur when a child node tries to find a parent node to communicate with. It is important to try to create a balanced network where all nodes have redundant paths, but without too many routers in close proximity to create interference.