ontrolled by a proliferation of non-interoperable remote controllers to be brought under the command of a single control unit. Protocol Stack The ZigBee 1.0 specification includes an upper layer protocol stack (Figure 10-7) building on the IEEE 802.15.4 PHY and MAC layer specifications that were finalised in May 2003. Logical network control, security and applications layer are optimised for time-critical applications, with very fast device wake-up and network association times, typically in the region of 15 and 30 ms respectively. ZigBee Application Framework Application Support Layer (APS) APS security Message Endpoint manager formatting multiplexing Network Application Layer (NWK) NWK security NWK message Routing Network manager broker manager manager 802.15.4 LLC 802.2 Type 1 LLC Logical Link Control Logical Link Control MAC (802.15.4) PHY (802.15.4) 868 / 915 MHz 2.4 GHz Figure 10-7: ZigBee Outline Protocol Stack Wireless PAN Standards Star links ZigBee ZigBee end devices coordinator ZigBee Mesh links end devices ZigBee router Figure 10-8: ZigBee Supported Topologies The network layer is responsible for the usual tasks of network start-up, associating, dissociating, address assignment to devices, security, frame routing, etc. Multiple network topologies are supported by the network layer, as shown in Figure 10-8. The mesh topology can extend a network to up to 64,000 nodes through the use of ZigBee routers, which achieve efficient routing using a request-response algorithm rather than the use of router tables. The general operating framework (GOF) is an integration layer linking the application and network layers, and maintains an overview of device descriptions and addresses, events, data formats and other information that is used by the applications to command and respond to networked devices. Finally, at the top of the stack and similar to Bluetooth, application profiles are defined to support specific usage modes. For example, a lighting profile would include sensors for light level and occupancy as well