Topologies

• A central cable (the backbone) which connects all devices to the network. • Terminators at each end of the cable to stop the signal bouncing back8

A bus setup does not allow two computers to transmit at the same time, this avoids collisions.

• Performance degrades with heavy traffic • A failure on the main cable stops the whole network working. • Low security as several computers use the same cable so can see all data transmissions

• Less expensive to install as it requires less wires/no additional hardware • Easier to set up due to less equipment used

• Local-area-networks consist of a number of devices connected by wires, on a single site/building. • They can transmit data very fast but only over short distances

Wide-area-network

• Consists of a central node either a switch or computer which acts as a router. • Has several wires attached to the central node to connect devices separately

• if one cable fails, the rest of the network isn’t affected • faults can easily be located because the separate wires can be tested. • Consistent performance even during heavy usage • Easy to add new devices • More secure, messages can be sent directly to the central node • No problems of collisions since each device has its own cable

• More costly as more wires are required - If the central node goes down, the whole network fails

• The switch records the address of each device connected to its ports by looking at the MAC addresses in the data it receives. • It builds a table, mapping each device to the port it is connected to • This means it can direct incoming data to the correct device by looking at the destination address in the incoming signal.

• the switch defaults to a hub behaviour and sends the signal out on all devices.

• A physical topology is the setup of the physical components such as wires/devices • A logical topology is how the data is transmitted/sent around the network

You could have a physical star topology but a logical bus topology. This is achieved through installing a bus transmission protocol onto the devices.

• Data can’t be transmitted at the same time so a device wanting to transmit data sends a broadcast message onto the wire that all other devices see. • Then the intended recipient accepts and processes the message.