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Lesson 4: �The internet

Year 7 – Networks: from semaphores to the Internet

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What is the internet?

Starter activity

What is the internet? What can it be used for (give one example)?

In pairs, write your answers on a sticky note.

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Lesson 4: The internet

Objectives

In this lesson, you will:

Define what the internet is
Explain how data travels between computers across the internet
Describe keywords such as ‘protocols’, ‘packets’, and ‘addressing’

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The internet explained

Activity 1

Watch the video:

https://www.youtube.com/watch?v=Dxcc6ycZ73M

Whilst watching, keep thinking about the starter questions.

What is the internet?

What do we use it for?

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The internet explained – Answers

Activity 1

What is the internet?

The internet is a worldwide network of computers.
It is the physical hardware, i.e. the cables, the routers, and other pieces of hardware used to connect devices together.
Any device connected to the internet is part of this network, for example:

Laptops
Games consoles
PCs
Tablets
Mobile phones

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The internet explained – Answers

Activity 1

What do we use it for?

There are many uses of the internet. Below are some of the most common uses:

Storing information (e.g. cloud storage)
Entertainment (e.g. streaming films, videos, and music)
Playing online games
Communication (e.g. email)
Playing online games
Online shopping
Social networking (e.g. Instagram)
Viewing websites

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Data transmission across continents

Activity 2

We now know that the internet is a global network of networks.

How are networks in the UK connected to networks in America?

Think, pair, share

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Data transmission across continents

Activity 2

Visit www.submarinecablemap.com

Name 2 countries that are connected by ‘Columbus-III’. How long is the cable?

Write your answer in the activity worksheet.

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Some learners may have discussed the use of satellites to connect a network in the UK to a network in America. Satellites are used to connect distant networks in some instances, particularly in remote locations where cables are not present, but it is not the most common way. 99% of internet data passing across continents travels through cables that lie on the seabed. These are faster and cheaper than satellites.

Ask the learners to visit www.submarinecablemap.com. Ask the learners to name two countries that are connected by ‘Columbus-III’, and how long the cable is. Learners will see the names of cables on the right-hand side of the web page. If they click on ‘Columbus-III’, it will reveal the answers. Learners should write their answers in the activity worksheet.

Answers: Columbus-III connects a number of countries together. Valid answers are: Portugal, Spain, United States, and Italy. It is 9,833 km long.

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Interesting facts

Activity 2

The first oceanic cable was laid in 1851 to connect telephones
99% of internet data is transmitted through cables under the oceans
Oceanic cables can be damaged by anchors, trawling fishing nets, and even shark bites!
The longest network is 39,000 kilometres

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A Packet’s Tale

Activity 3

In lesson 1, you learnt that in 2019, there are 27 billion devices connected to the internet.
How does a message from one device find its way to another device?
Watch this video to find out: https://www.youtube.com/watch?v=ewrBalT_eBM

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A Packet’s Tale – Summary

Activity 3

Networks send and receive messages in small units of data known as ‘packets’.
A single message may be too large to fit in one packet. It is often split into many packets.
Each packet contains a part of the message, an address of where it came from, and an address of where it is going. These addresses are known as ‘IP addresses’, and they are unique.

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IP addresses

Activity 4

An IP address is made up of 4 groups of numbers between 0 and 255, each separated by a full stop.
These are unique for every device on the internet.
Typically, this would be the address of the router that connects to the internet.

Example:

192.168.5.43

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My IP address

Activity 4

Demonstration: What is my IP address?

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Packets and routers

Activity 5

A router joins networks together across the internet and forwards packets from sender to receiver.
Packets will be sent in the correct order.
There are millions of routers on the internet.
Packets can take different routes on their way to to their destination.

Which internet routers will ALL packets pass through? (Hands up)

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HR

IR2

IR 1

IR6

IR3

IR4

IR5

IR7

HR = Home router

IR = Internet router

Remind the learners about the role of a router. Explain to them that a router joins networks together across the internet. It is important to emphasise at this stage that there are many different ways of getting from one place to another across the internet, and packets of data making up a single message may take different routes. Use the diagram to help illustrate this. For example, a packet travelling from the home router at the top of the diagram to the home router at the bottom of the diagram may travel through the internet routers 1,2,3,4, or it may travel through internet routers 1,7,3,4.

Packets are sent/passed on to the internet in the correct order, but may travel along different routes until they get to their destination.

Ask the question, “Which internet routers will ALL packets pass through?”

Answer: All packets will pass through internet router 1 and internet router 4. Others internet routers may not all be used, as alternative pathways exist.

Image sources:

House image: https://pixabay.com/vectors/apartment-building-construction-2872754/

House image 2: https://pixabay.com/vectors/home-house-icons-jims-card-1294564/

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Packets and routers

Activity 5

Packets can arrive in the wrong order.
If a message were read in the order in which the packets arrived, it may not make sense.
Example: Imagine that a message to be sent from device A to device B across the internet was “hello how are you?”

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Message sent: “hello how are you?”

Activity 5

The packets are split as follows:

Packet 1: “hello”

Packet 2: “how”

Packet 3: “are”

Packet 4: “you?”

Packets are received at their destination as follows:

Packet 1, Packet 3, Packet 4, Packet 2

What would this message be if the packets were read in the order in which they arrived? How might this problem be solved? (Think, pair, share)

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Packet ordering: The solution

Activity 5

The packet ‘header’ contains:

Sender IP address
Receiver IP address
Total number of packets and the sequence number of this particular packet

The packet ‘payload’ contains:

Part of the message to be sent (the data)

When the computer receives the packets, it waits until it has received all of them, and then reassembles the data into the correct order using the sequence number.

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Packet header

Sender IP 192.1.5.8

Receiver IP 205.9.4.3

Sequence 1 of 5

Payload: “hello”

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Packet ordering: The solution

Activity 5

Example of a 3-packet message: “How are you?”

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Packet header
Sender IP	192.1.5.8
Receiver IP	205.9.4.3
Sequence	1 of 3
Payload	“How”

Packet header
Sender IP	192.1.5.8
Receiver IP	205.9.4.3
Sequence	2 of 3
Payload	“are”

Packet header
Sender IP	192.1.5.8
Receiver IP	205.9.4.3
Sequence	3 of 3
Payload	“you?”

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Packet ordering: Fill in the blanks

Activity 6

You have a message to send between 2 devices using 4 packets (one for each word).

Sender IP address: 1.1.1.1
Receiver IP address: 2.2.2.2
Message: “What is your name?”

Some packets have been partially completed. Fill in the blanks.

Use your activity worksheet.

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Packet ordering: Fill in the blanks – Answers

Activity 6

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Packet header		Packet header		Packet header		Packet header
Sender IP	1.1.1.1	Sender IP	1.1.1.1	Sender IP	1.1.1.1	Sender IP	1.1.1.1
Receiver IP	2.2.2.2	Receiver IP	2.2.2.2	Receiver IP	2.2.2.2	Receiver IP	2.2.2.2
Sequence	1 of 4	Sequence	2 of 4	Sequence	3 of 4	Sequence	4 of 4
Payload	“What”	Payload	“is”	Payload	“your”	Payload	“name?”

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Internet Protocols: TCP and IP

Activity 7

Reminder: Computers follow a set of rules (protocols) to communicate with each other across a network.
During this lesson, you have been following two important Internet Protocols called ‘TCP’ and ‘IP’.
‘TCP’ stands for ‘Transmission Control Protocol’.
‘IP’ stands for ‘Internet Protocol’.

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TCP and IP:

Activity 7

Transmission Control Protocol:

Splits the messages sent across the internet into smaller pieces called ‘packets’
Assembles the packets in the correct order at the receiver end

IP:

A protocol to route the packets
Each device on the internet has an IP address that uniquely identifies it from all other devices

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Multiple choice questions

Plenary

What is the internet?

A set of rules to allow communication
A worldwide network of computers
A gateway on a network
A single network

Put the correct answer for each of the 4 questions in bold in your activity worksheet.

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Multiple choice questions

Plenary

2) Which of the following is NOT an internet activity?

Playing online games
Checking Instagram
Sending an email to a friend
Creating a local Microsoft PowerPoint presentation

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Multiple choice questions

Plenary

3) Which of the following best describes the structure of an IP address?

4 numbers ranging between 0 and 100, separated by dots
4 numbers ranging between 0 and 255, separated by dots
3 numbers ranging between 0 and 255, separated by dots
4 numbers ranging between 0 and 255, separated by dashes

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Multiple choice questions

Plenary

4) Which protocol splits the messages sent across the internet into smaller pieces called ‘packets’?

FTP
HTTP
IP
TCP

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Multiple choice questions – Answers

Plenary

What is the internet?

A set of rules to allow communication
A worldwide network of computers
A gateway on a network
A single network

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Multiple choice questions – Answers

Plenary

2) Which of the following is NOT an internet activity?

Playing online games
Checking Instagram
Sending an email to a friend
Creating a local Microsoft PowerPoint presentation

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Multiple choice questions – Answers

Plenary

3) Which of the following best describes the structure of an IP address?

4 numbers ranging between 0 and 100, separated by dots
4 numbers ranging between 0 and 255, separated by dots
3 numbers ranging between 0 and 255, separated by dots
4 numbers ranging between 0 and 255, separated by dashes

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Multiple choice questions – Answers

Plenary

4) Which protocol splits the messages sent across the internet into smaller pieces called ‘packets’?

FTP
HTTP
IP
TCP

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Homework: Multiple choice questions

Homework

You will be given a further 5 multiple choice questions about the internet. You need to identify the correct answer.

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Due: Next lesson

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Next lesson

Summary

In this lesson, you…

Learnt about the internet and how data is sent across it.

Next lesson, you will…

Learn about different internet services, and the difference between the internet and the World Wide Web.

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