1. LAN, WAN, and Network Topologies
Component 1
LAN, WAN, and Network Topologies

2. Starter: Pre-reading recap
What is a network?
Describe the features of a ring network
What is a LAN?
Describe the features of a bus network
What is a WAN?
Explain the difference between a LAN and WAN
What device is needed to connect to a wired network?
What is a topology?
What device is needed to connect to a wireless network?
Name 3 Network Topologies
Describe the features of a star network

3. Learning Intentions and Outcomes
Explain the characteristics of networks and the importance of different network types, including LAN and WAN.
Describe the importance of common network topologies, including ring, star, bus and mesh, and their advantages and disadvantages.
Explain the importance of connectivity, both wired and wireless.

4. Networks
A network is simply a collection of computers and equipment connected together.
The allow people to share files and resources
There are two main types of network
(LAN) Local Area Network
(WAN) Wide Area Network

5. LAN – Local Area Networks
A local area network (LAN) is defines as a collection of computers and peripheral devices (such as printers) connected together within a single site.
A site is not restricted to one building!
At school our network is classed as a LAN. It connects together all computers, printers and servers in multiple buildings.

6. WAN – Wide Area Networks
A WAN is a network, in which the computers systems are all located relatively distant from each other, for example, in different buildings all over the country or in different countries.
The Internet is an example of a WAN.
You will note that many LANs could be linked using a WAN.

7. Benefits of Networks: Communication
Using to communicate with colleagues
Using messaging systems to chat while you are working on other things
Transferring files between computers

8. Benefits of Networks: Sharing Resources
Sharing folders so that you can access files anywhere on the network from any computer and different people can access these files as needed
Sharing peripheral devices such as printers and scanners
Sharing an internet connection

9. Benefits of Networks: Centralised Management
User profiles and security can all be managed centrally
Software can be distributed across the network rather than having to install it on each individual computer
Users can use any PC on the network but still see their own files.

10. Disadvantages A network manager may need to be employed – expensive
Security problems – files sent between computers could spread a virus
Hackers can gain access to data more easily
If the server is down, all workstations on the network are affected
Initial cost of servers, communication devices, etc. can be expensive

11. Graded Exercises Complete questions 1-3 of the grade 4 exercises
Remember to be smart when using the Internet:
Wikipedia is often complicated – sometimes even I don’t understand!
BBC Bitesize, Teach ICT, and Revision World are better places to find your information!

12. What is a topology?
A topology is a description/diagram of how computers can be laid out and connected. There are only three basic topologies that are used but these can be combined in a large network

13. Bus Network
Computers are connected to a single backbone cable. The computers all share this one cable to transmit to each other and only one computer can transmit at a time.
This is fine if most of the time the network is not too busy. It can be very slow with lots of computers trying to transmit at the same time.

14. Bus Network Advantages Disadvantages
Easy to implement and add more computer systems to the network
Quick to set up – well suited for temporary networks
Cost-effective – less cabling
It is difficult to troubleshoot the bus
Limited cable length and number of stations – performance degrades as additional computers are added
If there is a problem with the main cable or connection, the entire network goes down
Low security – all computers on the bus can see all data transmissions
Proper termination is required
Data collisions are more likely, which causes the network to slow down. A collision is when two computers try to send a packet at the same time

15. Ring Network
Computers are connected to adjacent computers in a ring. Computers take turns in transmitting data. This is controlled by a token around the ring. Computers can only transmit when they have the token.

16. Ring Network Advantages Disadvantages
Data is quickly transferred without a bottleneck – consistent data transfer speeds
The transmission of data is relatively simple as packets travel in one direction only
Adding additional nodes has very little impact on bandwidth
It prevents network collisions.
If any of the computer systems fail, the ring is broken and data cannot be transmitted efficiently
If there is a problem with the main cable or connection, the entire network goes down
It is difficult to troubleshoot the ring
Because all nodes are wired together, to add a another you must temporarily shut down the network

17. Star Network
All of the computers have their own cable that connects them to a central computer. The central computer controls the network.
The central computer is usually a server, where resources are stored.

18. Star Network Advantages Disadvantages
Good performance/fast network speed
Easy to set up
Possible to add more computer systems without taking the network down
Any non-centralised failure will have very little effect on the network
Minimal network collisions
Better security
Expensive to install – more cabling required
Extra hardware required, such as a hub

19. Topologies in use.
In most offices and classrooms the Star topology is used.
The room might look like a bus network but in fact all of the computers have their own cable connected to one device.

20. Mixed topologies Most network use a mix of the three topologies
The most common are star and bus.

21. Group Activity
In groups of no more than 4 you are going to create a poster that explains a network topology.
Explain:
How the topology works
The advantages and disadvantages
You must include a diagram of the network

22. Graded Exercises Complete questions 4-6 of the Grade 4 exercises
Remember to be smart when using the Internet:
Wikipedia is often complicated – sometimes even I don’t understand!
BBC Bitesize, Teach ICT, and Revision World are better places to find your information!

23. Connectivity
To connect a computer system to a network, a Network Interface Card (NIC) is required. A physical hardware port allowing a cable to connect your computer system to the network provides one method of connection.
The second method is to connect a computer system using a wireless connection, called a Wi-Fi.

24. Network Interface Card
Each computer must have way to connect to the LAN. This is done via a Network card. The correct term for a network card is
Network Interface Card or NIC for short

25. WiFi Connectivity
Computers can make a wireless connection if they have a wireless NIC.
A wireless router provides a connection with the physical network.
A computer device needs to be within range of the router to get access.
A wireless connection uses radio signals to send data across networks.
The wireless adapter converts the data into a radio signal and the wireless receiver decodes it so that the computer can understand it.

26. Typical network speeds
Physical Connections
Wireless Connections
A physical connection may be made using:
a copper cable, with typical data transfer speeds of between 100 Megabits per second (Mbps) and 1 Gigabit per second (Gbps)
a fibre-optic connection which has typical data transfer speed of between 1-10 Gbps
Wi-Fi connections have typical data transfer rates of 54 – 108 Mbps. However, this can be severely affected by the distance between the device providing the Wi-Fi connection and computer systems.
The data transfer rates can also be severely affected by atmospheric conditions, in particular heavy rain.

27. Graded Exercises Complete the remainder of the graded exercises
We will self-assess Grade 4 in 10 minutes.
Remember to be smart when using the Internet:
Wikipedia is often complicated – sometimes even I don’t understand!
BBC Bitesize, Teach ICT, and Revision World are better places to find your information!

28. Crib Sheet – What I must remember about _______
Starting Point: Read the learning outcomes from the exam board
Record the key facts that you need to remember about LANs, WANs, and Network Topologies!
Think about what you have learnt today, what questions you have been asked, definitions of words, or anything else you think is important!

29. Homework Question Sheets: 35 Advantages of Using Networks
39 Network Topologies
Pre-reading notes:
Page (Packet Switching, Circuit Switching, Routing, MAC Addresses)