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Computer networks


Write down what you think of what you hear the word network.


Write down what you think the world wide web and Internet are. Is there a difference?

Learning Intentions

  • Explain what a network is

  • Be able to explain the difference between a LAN and WAN

  • Be able to describe transmission mediums

Success Criteria

  • I am able to demonstrate an understanding of how computers communicate and share information over networks

What is a network?

  • a group or system of interconnected people or things.
    Oxford Dictionary

How does the Internet work?

Pair And Share

  • Pair up with someone in the class and think about the video you have just seen.

  • Think of three points that you have learned from this video. 


  • Unfortunately, not everyone understands what the Internet is...

Networks are everywhere!

Examples of networks include:

  • The school network

  • Your home network

  • Government networks

  • Company networks

Breaking down networks

  • Networks can become very, very large. For example, the Internet is one of the largest networks serving almost 4.4 billion users as of 2019.

  • To be able to cope with this, rather than having a connection to each person’s individual computer, we use many smaller networks.

  • For instance, in your home you will probably have a small WiFi network that allows you to connect to the Internet.

Computer networks

  • Computers that are not on an network are called stand alone computers.

  • Computer networks are made up of multiple computers which all communicate using agreed protocols.

  • Each computer is given an IP address that allows the computer to uniquely identify itself.

Think of examples of computer networks around the world today.


Types of network

There are two main type of network:

  • Local Area Network (LAN) - E.g. your home network or the school network

  • Wide Area Network (WAN) - E.g. The Internet

Types of network

  • A LAN covers a small area such as a single room or a building and is usually owned by an individual or single company.
  • The school has a LAN that connects all of the computers within it together and on to a bigger network.

Types of network

  • A WAN covers a much larger area than a LAN. For example, a WAN may cover a whole country (e.g. BT or Sky Broadband) or a whole continent.
  • The Internet is an example of a WAN.
  • WANs are often made up of smaller LANs.

Transmission mediums

  • There are two formats of transmission media used to carry data:
    1. Wired (using a cable)
    2. Wireless (e.g. WiFi)
  • We talk about bandwidth being the amount of data which can be carried over a transmission medium at the one time.

Wired Transmission mediums

  • Wired networks can be wired together using different cabling, ranging from standard copper cables to more advanced optical fibre cables.

Advantages of networks

  • Allows sharing of data and files
  • Allows access to data and files anywhere on the network
  • Allows the sharing of devices such as printers (and saves money)
  • Allows for easy communication between users
  • Data can be easily backed up
  • Allows files to be stored in one secure location and only accessed on request

Disadvantages of networks

  • Cost – setting up a network can be expensive
    Managing a network can be difficult, especially as they get bigger.
  • If the network goes down, all users may end up suffering the consequences and may not be able to access their files.
  • Risk of hacking. Files on a network can be accessed remotely and if not secured correctly they could be stolen by a hacker.

LANs vs WANs

Advantages of LANs:

  • Allows sharing of expensive hardware
  • Allows fast transmission of files
  • Allows for reliable transfer of files
  • Allows computers to share one Internet connection

Advantages of WANs:

  • Allows data and files to be shared around the world
  • Allows users to remotely access their computers
  • Allows services such as ATMs (cash machines) to be connected directly to the bank’s network and accessed anywhere
  • Allows companies who are in different countries or continents to communicate as if they were in the same building

Communication across a network

Image from provided by Jamie Balfour

Communication across a network

Stages of sending data

The stages for sending data from one computer to another are:

  • Data is requested from the host computer (sender) by the user’s computer (receiver). The receiver tells the sender what it wants and tells the sender it’s IP address.

  • The sender packages the data into chunks or packets with the receiver’s IP address on them and sends them to the receiver at their IP address.

  • The receiver waits for the packets from the sender and rebuilds the data into the file


  • Firewalls are one of the most important forms of network security. A firewall checks incoming (and outgoing) packets before allowing them in or out of the network.
    They check that the packets are following a set of rules. They are also used to set rules about which application or system should receive the packets.

  • Rules are created that take account of the following:

    • sender (source) IP address

    • receiver (destination) IP

    • address

    • port numbers

    • protocols

Complete the questions in the worksheet

Prepare a short PowerPoint on networks. In this you should discuss LANs and WANs. You should also include firewalls.


Make sure to cover the key points that we went through today.


We will continue to build these PowerPoints as we continue with networks.


To summarise

Presentation Overview
Computer Networks
© 2020 - 2024 J Balfour
17:02 | 23-05-2024
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