Topologies

Question 1

What does a bus topology consist of?

Answer 1

• 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

Question 2

How do bus topologies avoid collisions?

Answer 2

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

Question 3

Disadvantages of bus topologies

Answer 3

• 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

Question 4

Advantages of bus topologies

Answer 4

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

Question 5

What is a LAN / WLAN?

Answer 5

• 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

Question 6

What is a WAN?

Answer 6

Wide-area-network

Question 7

What does a star topology consist of?

Answer 7

• 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

Question 8

Advantages of bus topologies

Answer 8

• 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

Question 9

Disadvantages of star topologies

Answer 9

• More costly as more wires are required

- If the central node goes down, the whole network fails

Question 10

How does a star topology operate?

Answer 10

• 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.

Question 11

What happens if the destination address is not in the switch’s table in a star topology?

Answer 11

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

Question 12

What is the difference between a physical and logical topology?

Answer 12

• 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

Question 13

Give an example of the logical and physical topologies being different and how this is achieved

Answer 13

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

Question 14

How does a bus topology operate?

Answer 14

• 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.