Network addressing
In a ZigBee network, each node must have a unique identification. For this purpose, each node has two addresses:
IEEE (MAC) address: A 64-bit address, allocated by the IEEE, which uniquely identifies the device. No two devices in the world can have the same IEEE address. It is often referred to as the MAC address. In a ZigBee network, it is sometimes called the ‘extended’ address.
Network address: A 16-bit address that identifies the node in the network and is local to that network. Thus, two nodes in separate networks may have the same network address. It is sometimes called the ‘short’ address.
In ZigBee PRO, the network address of a node is dynamically assigned as a random 16-bit value by the parent when the node first joins the network. This is known as stochastic addressing due to the randomness of the address allocation. Although random, the parent ensures that the chosen address has not already been assigned to one of its neighbors. In the unlikely event of the address already existing in the network beyond the immediate neighborhood, a mechanism exists to automatically detect and resolve the conflict. The allocated network address can be retained by the joining node, even if it later loses its parent and acquires a new parent.
The Coordinator always has the network address 0x0000.
While an application on a node may use IEEE/MAC addresses or network addresses to identify remote nodes, the ZigBee PRO stack always uses network addresses for this purpose. To facilitate translation between IEEE/MAC addresses and network addresses, an Address Map table may be maintained on the node, where each table entry contains the pair of addresses for a remote node.
In the NXP implementation of ZigBee PRO, the IEEE/MAC addresses (of other network nodes) are stored in a single place on a node, called the MAC Address table. This avoids the need to repeat the 64-bit IEEE/MAC addresses in other tables, such as the Address Map table and Neighbor table, and therefore saves storage space. Instead, a 16-bit index to the relevant entry in the MAC Address table is stored in the other tables.
It is also possible to define a 16-bit ‘group address’ which refers to a set of applications (or endpoints that may be located across several nodes. For details, refer to Section 3.4.1, Multiple applications and endpoints).
Specifying a group address in a data transfer results in the data being broadcast to all nodes in the network but, at the destinations, the data is only passed to those applications, which are covered by the group address. Refer to Section 6.3, Managing group addresses for more details of using group addresses.
Parent topic:Network level concepts