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Lesson 1: Computer networks and protocols

Year 7 – Networks: from semaphores to the Internet

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How many devices are connected to the internet?

Starter activity

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Lesson 1: Computer networks and protocols

Objectives

In this lesson, you will:

Define what a computer network is and explain how data is transmitted between computers across networks
Define ‘protocol’ and provide examples of non-networking protocols

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Historic communication methods

Activity 1

These are all forms of communication. Can you match the name with the image and the year in which they were first used?

Email

Carrier pigeon

Telephone

Semaphore

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1961

1876

1837

1167

1791

This slide shows five communication methods, five images, and five years. Learners need to identify which method goes with which image and year. The activity is also provided in the worksheet for pupils to complete electronically, if required.

Image sources:

Pigeon image: https://pixabay.com/vectors/pigeon-animal-bird-wings-feathers-24418/

Telegram image: https://pixabay.com/vectors/code-communication-hand-history-1295854/

Email image: https://pixabay.com/illustrations/mail-message-email-send-message-1454731/

Telephone image: https://pixabay.com/illustrations/retro-telephone-dial-phone-vintage-4273184/

Semaphore image 1: https://en.wikipedia.org/wiki/Semaphore_telegraph#/media/File:Chappe_semaphore.jpg

Semaphore image 2: https://en.wikipedia.org/wiki/Semaphore_telegraph#/media/File:Chappe.svg

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Answers

Activity 1

Carrier pigeon

Semaphore

Telephone

Email

5

1961

1876

1837

1167

1791

These are all forms of communication that involve passing a message on between multiple operators or devices until the message is received by the recipient. A computer network operates in the same way.

Interesting facts about each communication method that you could share:

Carrier pigeon: Carrier or homing pigeons are birds that have been trained to find their way back home over great distances. Carrier pigeons were used historically to send short messages on a small piece of paper attached to the leg of the bird. They were used in battle by armies to communicate. Some pigeons can fly at over 60 mph. By 1167, a regular carrier pigeon communication service had been created between Baghdad and Syria. Over 54,000 pigeons were used in WW1 and WW2 to relay secret messages.
Semaphore: The semaphore was first introduced in France in 1791, when France was on the brink of a revolution. The French government needed a way to send and receive messages quickly. Claude Chappe (along with his 4 brothers) created a system that was made of towers placed less than 20 miles apart. Each tower had two moving wooden arms and a crossbar. The position of these arms and the crossbar could be changed, and 196 different symbols were created based on these differing positions. A signal displayed by one tower would be observed by an operator using a telescope at the next tower, who would then make the same signal for the next tower — and so the message was sent from tower to tower. Operators needed to check their nearest towers very regularly and re-create the signal as quickly as possible. It was a very tiring job.
Telegrams: In 1837, two sets of inventors simultaneously developed an electrical telegraph: Wheatstone and Cooke in England, and Samuel Morse in the United States. Morse went on to develop an alphabet using dots and dashes that became known as ‘Morse code’. By 1861, this Morse telegraph system connected the West and East Coast of America.
Telephone: Alexander Graham Bell is commonly credited as the inventor of the telephone, though many individuals contributed to the devices that we use today. Alexander Graham Bell filed for the patent of the telephone system in 1876.
Email: 1961: The very first version of what we now know as email was created in 1965 at Massachusetts Institute of Technology (MIT). This allowed users to share files and messages on a central disk on a server, logging in from remote machines. In 2019, there are 293.6 billion emails sent every day. In 2023, more than 347.3 billion emails will be sent daily. At least half of all emails are spam. (Source: https://www.statista.com)

Image sources:

Pigeon image: https://pixabay.com/vectors/pigeon-animal-bird-wings-feathers-24418/

Message in a bottle image: https://pixabay.com/vectors/message-in-a-bottle-drift-bottle-154178/

Telegram image: https://pixabay.com/vectors/code-communication-hand-history-1295854/

Email image: https://pixabay.com/illustrations/mail-message-email-send-message-1454731/

Telephone image: https://pixabay.com/illustrations/retro-telephone-dial-phone-vintage-4273184/

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What is a computer network?

Activity 2

A computer network is when two or more computers are connected together to allow them to communicate.

This brings many benefits, which will be covered later on.

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Using computer networks

Activity 2

What common daily activities do you think use computer networks?

Think, pair, share

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How many common daily activities do you think use computer networks?

Activity 2

Morning: music playing via a Bluetooth speaker, asking Alexa for the weather forecast, controlling your central heating via an app on your phone

Daytime: logging on to a PC for a Computing lesson, accessing files stored on the school network, printing to the library printer, researching a topic on the internet

Evening: Using social media, playing games online

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Key milestones

Activity 3

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1999

Mini computers: Nokia introduced a mobile phone that could connect to the internet.

1989

World Wide Web: �Tim Berners-Lee invented the WWW.

1974–1977

The first personal computers: IBM and Apple were a couple of the brands releasing PCs.

1969

The internet: The first internet was called the ARPANET. Only a few people had access to it initially.

Question revisited:

How many devices are now connected to the internet?

Guidance: There are just under 8 billion people on the planet.

Think, pair, share

1950–1970

Mainframe computers: Mainframe computers grew in popularity. These were large and expensive.

Computers have evolved greatly over the last 70 years. Discuss the timeline with your learners. This shows some key milestones in the growth of computer networking.

1950–1970: Mainframe computers grew in popularity. These were single computers supporting multiple users/terminals connecting to it at the same time. These machines were very large and expensive.

1969: The internet was brought online in 1969. It was initially called the ARPANET. It was a project run by the Advanced Research Projects Agency (ARPA) to connect four American universities together.

1989: A British scientist called Tim Berners-Lee invented the World Wide Web in 1989. The original purpose of the web was to allow automatic information sharing between scientists in different universities around the world.

1999: Nokia brought out a revolutionary new mobile phone called the 7110. This was the world’s first mobile phone that could access information from the internet. The mobile phone became a global communication device. Users could check weather reports as well as email. However, all information was text only.

Learners should now have a basic overview of how computer networks have evolved over time. Now, ask your learners the same question that was asked at the very start of the lesson, “How many devices are now connected to the internet?”. Ask them to review their answers, then to pair with a neighbour and discuss their answers with each other. If they are struggling to think of an answer, you could inform them that there are currently around 8 billion people on the planet. You could also mention that many devices now connected to the internet require no human-to-computer interaction; they are communicating with themselves independently. This is known as the Internet of Things (IoT) and includes devices such as smart meters sending gas and electric readings each day from our homes to our providers. If the learners’ answers differ from the start of the lesson, ask them to amend them. The answer will be revealed at the end of the lesson.

Image sources:

PC image: https://en.wikipedia.org/wiki/BBC_Micro#/media/File:BBC_Micro_Front_Restored.jpg

Word Wide Web image: https://commons.wikimedia.org/wiki/File:Emojione_1F310.svg

Nokia 7110 image: https://en.wikipedia.org/wiki/Nokia_7110#/media/File:Nokia_7110_open.png

Mainframe image: https://commons.wikimedia.org/wiki/File:IBM_Electronic_Data_Processing_Machine_-_GPN-2000-001881.jpg

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A message to Australia (part 1)

Activity 4

Imagine that you needed to send a message from the UK to Australia but no computer networks exist.

What methods would you use?
What information would you need?
Would anyone be involved in relaying the message?

Think, pair, share

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Ask the learners to discuss how they might send a message from their location to a person in Australia without the use of computer networks. Ask the learners to try to think of multiple methods, as well as the information that they would need in order to get the message to the intended recipient in Australia.

The simplest discussions might focus on an individual writing a message and then travelling from the UK to Australia to deliver it (via car, plane, or boat, etc.). More complex discussions might involve using more than one person in different countries on the way to Australia, who can each travel a short distance before passing it on to the next person in line. For this scenario, the recipient’s name and address would need to be included with the message. This would be one of the rules of the communication. Discussions may also include communication methods mentioned in activity 1, such as carrier pigeon.

Image sources:

Message image: https://pixabay.com/vectors/message-private-message-mail-email-369540/

UK image: https://svgsilh.com/image/36481.html

Australia image: https://svgsilh.com/image/157273.html

Computer icon: http://www.freestockphotos.biz/stockphoto/15372

Prohibited icon: https://pixabay.com/vectors/no-symbol-prohibition-sign-39767/

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A message to Australia (part 2)

Activity 4

Imagine that you needed to send a message from the UK to Australia and computer networks do exist.

What methods would you use?
What information would you need?
Would anyone be involved in relaying the message?

Think, pair, share

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Message transmission: letters

Activity 4

An answer to the first scenario (no computer networks) might have been to write and post a letter.

How is a letter sent from the UK to Australia? What steps are involved between putting the letter in the postbox and it arriving at the destination?

(Hands up)

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Message transmission: email

Activity 4

Just as a letter does not go directly from the sender to the recipient, the email does not travel from a sender’s machine through a cable or “into the cloud” directly to the recipient’s machine.

The message is passed on to many mail servers along the way, who help get the message to its destination.

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Hopefully, a common answer to the second scenario, where computer networks existed, was “email”. A common misconception is that a message is transmitted directly from one machine to another across a network or the internet. Learners may believe that when an email is sent, it simply ‘enters the cloud’ and then appears at the recipient’s machine, or that it travels directly along a cable from point A to point B. This is not the case.

The purpose of this slide is to illustrate that a message may pass through many intermediary devices along the way, that then pass the message on. This is exactly the same as how a letter may travel across a country or the globe, going from one post office depot to another until it reaches the recipient. Indeed, this is the same principle as the semaphore in activity 1, which used towers positioned a visible distance apart to relay a signal via the positioning of the towers’ wooden paddles.

Image sources:

Message image: https://pixabay.com/vectors/message-private-message-mail-email-369540/

UK image: https://svgsilh.com/image/36481.html

Australia image: https://svgsilh.com/image/157273.html

Computer icon: http://www.freestockphotos.biz/stockphoto/15372

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Protocols

Activity 5

All methods of communication need rules in place in order to pass on the message successfully. These sets of rules are called protocols.

What protocol exists for meeting someone new?

Is this the same in all countries?

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Protocols

Activity 5

UK:

Smile, and say ‘Hello’
Shake right hands (shaking left hands is considered disrespectful in many countries)

Question:

In which cultures do people use the below protocols to greet each other?

Bowing
Rubbing noses
Sticking your tongue out

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Protocols

Activity 5

Question: In which cultures do people use the below protocols to greet each other?

Answer:

Bowing: Japan
Rubbing noses: Inuit
Sticking your tongue out: Tibetan

It is important that both parties involved in communication know the rules. This is the same with computer network protocols.

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Climber and belayer protocol

Activity 6

Climbers often attach to a rope for safety via a belay clip.

The length of this rope is controlled by a person called the belayer.

The belayer is responsible for the climber’s safety.

A series of commands exist in order for the climber and belayer to communicate during the climb.

Can you order them correctly so that the climber can ascend safely?

Belay: To fix a rope around an object to secure it

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Commands to order

Activity 6

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Command	Person	Meaning
Belay On	Belayer	The rope is secured and slack taken up so it is tight.
Climbing	Climber	I wish to climb.
Off Belay	Climber	I wish to be detached from the rope. The climber only says this command when it is safe to do so at their destination.
Belay Off	Belayer	The belay rope has been disconnected.
Climb On	Belayer	I am happy for you to climb.
Slack	Climber	I need some slack rope in order to climb up.
On Belay?	Climber	Is the rope secured?

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Answers

Activity 6

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Command	Person	Meaning	Order number (1 to 7)
On Belay?	Climber	Is the rope secured?	1
Belay On	Belayer	The rope is secured and slack taken up so it is tight.	2
Climbing	Climber	I wish to climb.	3
Climb On	Belayer	I am happy for you to climb.	4
Slack	Climber	I need some slack rope in order to climb up.	5
Off Belay	Climber	I wish to be detached from the rope. The climber only says this command when it is safe to do so at their destination.	6
Belay Off	Belayer	The belay rope has been disconnected.	7

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Computer protocols: email and web address protocols

Activity 7

What rules (protocols) exist for an email address?

An ‘@’ symbol must be used.

The email address must be unique.

What parts of this web address show rules (protocols) being used?

http://www.bbc.co.uk

All website addresses start with ‘http://’ followed by ‘www’.

All website addresses are unique.

They use dots to separate each part of the address.

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How many devices are connected to the internet?

Plenary

Would you like to revise your answer in the light of the lesson?

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Answer: Over 27 billion

Plenary

Answer:

There are currently just under 8 billion people on the planet. In 2019, the number of connected devices on the internet reached 27 billion! A projected 75 billion will be online by 2025 (statista.com).

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Next lesson

Summary

In this lesson, you…

Defined what a computer network is and explained how data is transmitted between computers across networks.

Defined a protocol and looked at examples of non-networking protocols.

Next lesson, you will…

Look at the hardware necessary for connecting devices to networks.

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