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Objectives
• Define a computer network
• Router and its functions
• Network devices:
– Network interface cards (NIC)
– Hubs
– Bridges
– Switches
– Modems
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Computer Network
A network is two or more computers, or
other electronic devices, connected
together for sharing resources.
Computer Network
The most common resource shared today is
connection to the Internet.
Other shared resources can include a printer
or a file server.
Network can range from a few computers to
large network such as internet
Devices such as hubs, switches etc. are
needed to distribute data within a network
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Network Devices -
Connect a group of devices to form a
LAN
It has cables plugged into it from each
computer.
Network Devices -
It receives a data packet at one of its ports and
broadcast it to every computer in the network
It is not secure and very efficient method of data
distribution
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Network Devices -
Used to connect two LANs (or parts of
LAN) that uses same protocols
(communication rules)
Network Devices -
Connect a group of devices to form a
LAN
It has cables plugged into it from each
computer.
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Network Devices -
Each device on a network has a unique MAC (Media Access
Control) address.
A Switch can identify the MAC address of data packets of
sender and receiver systems
It sends the data to the appropriate computer(s) only.
Using switch is a secure way of distributing data over a
network.
Network Devices -
A router provides a link between two or more networks.
Routers work together to direct data packets to their correct destination.
Routers can:
Make decisions about whether a message should be passed between the
networks
Make the format of the message suitable for the new network
Read the information about the message and decide not only where the
message should be going but also decide the best route that can be taken for it
to get there.
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Data Packets
Message carried via network
Consists of:
• Header for identification
• Sender’s IP address
• Receiver’s IP address
• No. of data packets that make up whole message
• Identity number of each packet
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Network Devices -
Modulator-DEModulator
It enables a computer to transmit data over, for
example, telephone or cable lines.
Computer information is stored digitally, whereas
information transmitted over telephone lines is
transmitted in the form of analog waves.
A modem converts between these two forms.
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Network Devices -
Network Interface Card
Allows a device to connect to a network
Usually part of the device hardware and
frequently contains MAC address
generated at the manufacturing stage.
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Other hardware -
Used for wired networks
Faster Data transfer rates
Secured than wireless networks
Cables can be either copper or fibre optics.
Fibre optics offer higher data transfer rate and
better security.
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Further Reading/Online References
https://www.youtube.com/watch?v=1z0ULvg_pW8&t=5s
https://www.youtube.com/watch?v=M4Nf2-g4LzE
https://www.youtube.com/watch?v=Mad4kQ5835Y
https://www.teach-ict.com/gcse_new/networks/hardware/miniweb/index.htm
https://www.ictlounge.com/html/network_hardware.htm
Network hardware
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Exam Style Questions
1. Ken owns a large shop with a number of computers. He
would like each computer to be able to access the internet to
enable new orders to be processed and to answer customer
queries.
Give three items of hardware Ken may need to buy to set up
a computer network.
2. Give the name of the device that is used so that several
computers can you home can all share a single internet
connection.
3. Explain the main difference between the network devices
hub and switch.
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Objectives
Use of Wi-Fi and Bluetooth in networks
Connecting devices using Wi-Fi and
Bluetooth
Similarities and differences between Wi-Fi
and Bluetooth
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• Enables computers and other devices to
communicate wirelessly with each other
• Wireless transmitter receives information from
a network via its connection, converts it into
radio waves and then transmits them
• Areas where internet can be accessed wirelessly
using Wi-Fi are called Access Points or Hotspots
• Signal range depends on the type of wireless
router and also obstacles in the way of the
signal
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• Advantages
You are not confined to a fixed place to
access the network
Fewer/no trailing wires to trip over
Less wires – less installation costs
• Disadvantages
Danger of hackers reading messages
Wireless signals may be weak in certain
areas
Recent research shows evidences of health
risks 19
• Wireless technology used to exchange data
over short distances using radio waves
• Paired devices using Bluetooth pick up one of
the 79 channels at random for data transfer
• Used for short distances, where data transfer
speed is not crucial and low bandwidth
applications (smaller files)
• Applications – input/output devices, mobile
phones, game controllers
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Bluetooth Wi-Fi
Wireless technology: Wireless technology: Communication using
Communication using radio waves radio waves
Has high signal range upto 100 mts Lower signal range of 10 mts
Devices cannot communicate
Devices can communicate directly
directly
Supports many users Supports fewer users
High level security support Low level security
Fast data transfer Slow data transfer
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Tethering
Tethering is a process/way to share your phone's
internet connection with other devices like laptops
or tablets.
Tethering can be accomplished through several
methods including Bluetooth, universal serial bus
(USB), or Wi-Fi hotspot.
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Some essential parts of a network
Web Browser Software
Program that allows to view web pages stored on
the internet
Web browsers interpret the HTML codes in the
web page
Web browsers allow the user to find information
on web pages and websites via:
• Entering s web address (URL)
• Keyword searches
• Hyperlinks
• Menus
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Exam style questions
Bluetooth is a method that allows devices to communicate with
each other and pass data.
a. Give the names of two pairs of devices that communicate
using Bluetooth. [2]
b. Explain one advantage and one disadvantage of using
communicating using Bluetooth. [2]
Next Generation School is planning to set up a computer lab for
their newly constructed academic block. The computer lab needs
to be networked with an access to internet as well.
a. Explain how to set up this lab. [4]
State any one similarities and two differences between WiFi and
Bluetooth technologies . [3]
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Further reading/References
• https://www.bbc.co.uk/bitesize/guides/ztyd3k7/revision/9
• https://www.teach-ict.com/gcse_new/communication/wi-fi_bluetooth/miniweb/index.htm
• https://www.diffen.com/difference/Bluetooth_vs_Wifi
• https://www.ictlounge.com/html/bluetooth_wi-fi.htm
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Cloud Computing
• Cloud computing is the on-demand delivery of
computing resources (such as storage and infrastructure),
as services over the internet.
• Resources are housed in powerful remote computers
called Servers
• Cloud computing allows users to access and use
applications such as word processors, spreadsheets
stored on remote servers
• Cloud computing eliminates the need for individuals and
businesses to self-manage physical resources themselves,
and only pay for what they use.
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Cloud Computing - Advantages
Lower maintenance costs: Hardware & Software does not need
to be purchased, installed, maintained or upgraded on the local
computer/server
Pay as per usage: Software does not have to be purchased and
only have to pay for the parts they use (Software as a service)
Automatic upgradation of software
Users can access the resources anywhere and in any device with
internet connection available
Automatic back up of data remotely
Collaboration – Users can share, collaborate on same
documents
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Cloud Computing - Disadvantages
Internet access required
Upload and download speed depends on internet
speed and service provider
Users or organization should be reliant on service
providers to maintain access, upgrade, backup etc.
Could be risky for confidential data as users will have
less control over the data. This can be solved by using
private clouds
Service providers may be targeted by hackers
Sharing data during collaboration may breach data
protection acts in some countries
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Cloud Computing - Disadvantages
Internet access required
Upload and download speed depends on internet
speed and service provider
Users or organization should be reliant on service
providers to maintain access, upgrade, backup etc.
Could be risky for confidential data as users will have
less control over the data. This can be solved by using
private clouds
Service providers may be targeted by hackers
Sharing data during collaboration may breach data
protection acts in some countries
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Exam style questions
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• Global network of interconnected computer networks.
• Used to connect people, communities and countries
worldwide.
• Internet allows the users to access webpage
• Business can use internet for information retrieval,
communication, marketing, sales, banking.
• Internet uses a set of rules or protocols called TCP/IP
(Transmission Control Protocol/Internet Protocol). Hence
devices using internet requires to have a unique IP address
(Eg: 192.168.1.5) to communicate. 31
• A private network that is used inside an organisation
makes use of web pages, browsers and other internet
technologies.
• Intranet provides restricted access to the information
compared to the Internet
• Parts of an intranet can be made available to anyone in
the organization while some part of it consisting
sensitive information can be made available to certain
people only.
• The restriction is achieved usually by means of username
and passwords
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• An intranet that allows users from other organization to
use it for specific purposes.
• Examples of Intranet:
– School intranet that allow access to parents to communicate
and view academic progress of their wards
– Hospital intranet that allow access to community doctors to
book appointments for patients
– Manufacturing company intranets that allows access to
distributors for ordering and pricing information
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INTERNET INTRANET
INTERnational NETwork INTernal Restricted Access NETwork
Information concerning a particular organisation that
Information about everything
has set it up
Can be used by anyone Used by employees, stake holders of the organization
Certain websites outside the internal network can be
Difficult to restrict the access
blocked/restricted
Secure from hackers as they are usually behind the
Less secured
firewall
No authentication necessary Authentication required for access
Can be accessed from anywhere Can be accessed from agreed points
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Further reading/References
https://www.igcseict.info/theory/4/index.html
https://www.teach-ict.com/gcse_new/gcse_ict_home.html
https://www.ictlounge.com/html/networks.htm
https://igcseictweb.wordpress.com/4-2-computer-networks/
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Exam style questions
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LAN WAN
Local Area Network Wide Area Network
Covers a wide geographical area (Eg:
Confined to small area
between cities, countries or continents)
Uses more expensive
Uses cable, wireless, infra-red
telecommunication, satellite links that
and microwave links which are
are supplied by telecommunication
owned by organization
companies.
Less expensive to build as More expensive to build as
equipments are owned by the sophisticated communication systems
organisation which are cheaper are used involving rental of
than rented lines and equipments communication lines
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• Wireless Local Area Network
• Computers/Devices are able to communicate
wirelessly
• Uses are able to move around but can still be
connected to the network/Internet
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ADVANTAGES DISADVANTAGES
Cheaper than wired LAN and less cabling Not suitable in areas where the wireless signal
is needed is too weak
Expansion of the network is easier – more
Security issues as the radio signals may be
devices such as printers, scanners can be
intercepted by hackers
linked easily.
Users can work anywhere in the building Wireless signals are not reliable as wired
where the wireless signal is available cables
Data transfer speed is lower than cabled
network
Interference from other electrical and
electronic equipment used in the same
building may disrupt the wireless signal
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Exam style questions
Give two benefits of using local area network. [2]
Describe one difference between LAN and WAN. [1]
A school is currently thinking of replacing their wired LAN with
a WLAN.
Explain the differences between a wired LAN and a WLAN. [2]
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