 active hub, also known as a repeater, is a variety of passive hub that also amplifies the data signal to improve signal strength over long network connections. For some PAN technologies, such as USB, star and tree topologies can be built without the need for specialised hardware, Figure 3-2: Star and Tree Topologies Wireless Network Physical Architecture Passive hub First PC Scanner Second PC Printer Figure 3-3: A Passive Hub in a Physical Star Network because of the daisy-chaining capability of individual devices (see Figure 2-11). An active or passive hub in a star topology LAN transmits every received data packet to every connected device. Each device checks every packet and decodes those identified by the device's MAC address. The disadvantage of this arrangement is that the bandwidth of the network is shared among all devices, as shown in Figure 3-3. For example, if two PCs are connected through a 10 Mbps passive hub, each will have on average 5 Mbps of bandwidth available to it. If the first PC is transmitting data, the hub relays the data packets on to all other devices in the network. Any other device on the network will have to wait its turn to transmit data. A switching hub (or simply a switch) overcomes this bandwidth sharing limitation by only transmitting a data packet to the device to which it is addressed. Compared to a non-switching hub, this requires increased memory and processing capability, but results in a significant improvement in network capacity. The first PC (Figure 3-4) is transmitting data stream A to the printer and the switch directs these data packets only to the addressed device. At the same time, the scanner is sending data stream B to the second PC. Chapter Three Switching hub First PC Scanner Second PC Printer Figure 3-4: Switching Hub in Physical Star Network. The switch is able to process both data stream concurrently, SO that the full network bandwidth is available to every device. Wireless Network Topologies Point to Point Connections The simple point to point connection sh