Network Topology

Overview

CraigNDave

https://www.youtube.com/watch?v=Fzho2mQQEuU&list=PLCiOXwirraUDvVsza-xO2mMwW9QBIa_FG&index=0

Computer Science Tutor

https://www.youtube.com/watch?v=iiU06wkTAuY&list=PL04uZ7242_M6O_6ITD6ncf7EonVHyBeCm&index=28

TRC PowerPoint

Network Topology

Star Topology

Nodes are connected to a host computer or hub that controls communication between devices. the hub or host computer regenerates any signal that it receives and passes it on. Only the intended recipient computer acts on the message.

All nodes have independent connections to the host. A cable failure on one branch of the network will continue to function normally and the failure will be easy to isolate.

Advantages	Disadvantages
· Adding new devices is easy and doesn't disrupt the rest of the network.	· It requires a lot of cables.
· There are no data collisions.	· It is expensive to install.
· There is less traffic on the network.	· Needs professionals to maintain and up keep.
· A cable failure on one branch of the network will be easy to isolate.

Bus Topology

When the bus (or line) topology is used each workstation is connected to a single cable (or backbone) which links all of the workstations.

The servers are connected to the main bus for data distribution to all the workstations.

Data can be transmitted in either directed along the main cable and workstations can communicate with other workstations.

A range of peripherals can also be connected to the main bus for shared usage. This could be a printer for example.

Advantages	Disadvantages
·Is cheaper to install as it used the least cable as the cost of network cabling (particular fibre optic), and the cost of the network cable installation can be significant	·If there is heavy traffic the system performance will fall off dramatically
.	·Data collisions due to shared cable
.	.Problems can be difficult to isolate

Data Collisions - CSMA/CD

CSMA/CD stands for Carrier Sense Multiple Access/Collision Detection. It is the protocol for carrier transmission access in ethernet networks. If two devices try to send a frame at the same time, a collision occurs and the frames are discarded. Each devices then waits a random amount of time and retries until the transmission is successfully sent.

Logical Bus Topology

A network could be wired using a star topology, but could act like a bus topology if all data traffic is sent to all machines.

Revision Questions

Question 1

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Question 2

1. What is bus Topology?

	Multiple Nodes are connected to a host computer
→	No
	Each computer is connected to 1 main linear cable.
	Its the customer service in the bus station
→	Not that bus.
	A bus prevents data collisions.
→	WRONG
	Your closest bus stop
→	NO
	A host computer that controls all devices
→	Bad

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Question 3

1. In a bus topology, all devices use different cables for connection.

	False.
	True.

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Question 4

1. State one advantage of the star topology over the bus topology network:

	Uses the least amount of cables
→	Incorrect: All nodes are connected by their own wire to the hub
	No data collision
→	Correct: Because all nodes don't use one wire for the backbone of transferring data
	Is the cheapest to make
→	Incorrect: Requires more wires which is more expensive
	Does not require to install a hub or switch
→	Incorrect: The hub is the central point of which all nodes connect to

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Question 5

1. What are the differences between a switch and a hub?

	A hub sends signals to the switch.
→	No
	Switches maintain a list of devices that it has encountered before.
→	If a device is on the list and is the intended recipient of a message, the message will only be transmitted to the device.
	A hub contains all of your favourite shows for only £9.99 paid bi-monthly, what a steal.
→	Not a hub.
	A switch prevents data collisions.
→	Both hubs and switches prevent data collisions.
	A hub will transmit data to all devices
→	Yes
	A switch will never transmit to all devices
→	A switch will transmit to all devices if it hasn't ever encountered the intended recipient of the data.

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Question 6

1. What is a star topology?

	All nodes are connected to each other.
→	That is a mesh topology
	All nodes are connected by one wire.
→	That is a bus topology.
	All nodes are connected to a central switch or hub.
→	Epic. The hub broadcasts all messages, whereas a switch sends to only the intended recipient.
	The nodes are arranged in a star shape.
→	Bruh. This isn't even a topology.

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Question 7

1. What is a bus topology?

	Uses may cables to transmit data
→	This is incorrect, a bus topology uses a single main cable as a backbone
	Uses one main cable as a backbone to transmit data
→	This is correct
	Connected devices in a network where each workstation has a dedicated cable to a central computer or switch
→	This is a star topology. A bus network uses one main cable as a backbone to transmit data
	A wire with a bus in it
→	This is very wrong, a bus topology uses a single main cable as a backbone to transmit data

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Question 8

1. What network topology connects all nodes via a central device?

	Mesh Topology.
→	Incorrect, mesh topologies have no central device.
	Bus Topology.
→	Incorrect, bus topologies utilise a main cable rather than a central device.
	Ring Topology.
→	Incorrect, ring topologies use no central device, instead connecting each device consecutively.
	Star Topology.
→	Correct, star topologies utilise a central hub or switch.

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Question 9

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Question 10

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Question 11

1. Which one of these is an advantage of star topologies?

	Adding new devices is easy and doesn't disrupt the rest of the network.
→	Correct answer
	It requires a lot of cables.
→	The correct answer was "Adding new devices is easy and doesn't disrupt the rest of the network."
	It is expensive to install.
→	The correct answer was "Adding new devices is easy and doesn't disrupt the rest of the network."
	Needs professionals to maintain and up keep.
→	The correct answer was "Adding new devices is easy and doesn't disrupt the rest of the network."

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Question 12

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