6: ZigBee Initialisation and Operation > Device and Service Discovery

Device and Service Discovery

The ZigBee specification provides the facility for devices to find out information about other nodes in a network, such as their addresses, which types of applications are running on them, their power source and sleep behaviour. This information is stored in descriptors on each node, and is used by the enquiring node to tailor its behaviour to the requirements of the network.

Discovery is typically used when a node is being introduced into a user-configured network, such as a domestic security or lighting control system. Once the device has joined the network, its integration into the network may require the user to start the integration process by pressing a button or similar. The first task is to find out if there are any other devices that it can talk to. For example, a device implementing the switch conforming to the HCL profile tries to find devices containing HCL load controllers to which it could potentially send its switch state information (the process of associating the switch with a particular load controller is handled by the binding process, presented earlier in this course).

There are two types of discovery, Device and Service Discovery:

Device Discovery

Device Discovery involves interrogating a remote node for address information. The retrieved information can be either:

• the MAC (IEEE) address of the node with a given network address
• the network address of the node with a given MAC address.

If the node being interrogated is a Router or Co-ordinator, it may optionally supply the addresses of all the devices that are associated with it, as well as its own address. In this way, it is possible to discover all the devices in a network by requesting this information from the Co-ordinator and then using the list of addresses corresponding to the children of the Co-ordinator to launch queries about their child nodes.

Service Discovery

Service discovery involves interrogating a remote node for information about its capabilities. This information is stored in a number of descriptors on the remote node, and includes:

• The device type and capabilities of the node (Node Descriptor)
• The power characteristics of the node (Node Power Descriptor)
• Information about each application running on the node (Simple Descriptor)

Requests for these descriptors are made by a device during its configuration and integration into a ZigBee network.

Click "Next Page" to continue.