Lesson video

Hello, my name is Mrs. Holbrook, and welcome to Computing.

I'm so pleased you decided to join me for the lesson today.

We are going to look at how information is transmitted over the internet, and how protocols can be used to secure communication.

Welcome to today's lesson from the unit: Computer Networks and Data Transmission.

This lesson is called Exploring the World Wide Web, and by the end of today's lesson, you'll be able to explain how the components of the World Wide Web work together to display web pages.

Shall we make a start? We will be exploring these keywords during today's lesson.

Web server.

Web server, a networked computer that stores and provides webpage and other data on request.

Packet, packet.

A segment of data, usually part of a larger message.

HTTP, HTTP.

The Hypertext Transfer Protocol is a set of rules that allows data such as webpages to be sent and received across the World Wide Web.

HTTPS, HTTPS.

The Hypertext Transfer Protocol Secure is a set of rules to allow data to be encrypted and exchanged securely via the World Wide Web.

There are two main parts to today's lesson.

We'll start by explaining how data is transmitted using packets, and then we'll move on to describe how protocols secure communication.

Let's make a start by explaining how data is transmitted using packets.

A huge amount of data is sent through the internet every day.

This data may travel through many devices to get to its destination.

Remember, the internet is a network of connected networks.

When you type in a web address or click a link, your web browser sends a message to the web server to ask for the data for that page.

So here in the diagram, we can see your computer with your web browser.

We've got the website with example.

com that goes out across the internet, connects to the web server and asks for the data for that page.

The web server receives the message, and then sends the data for the page back to the web browser to display.

Sophia's got a really good question.

Is all of the data for the whole page sent in one go? Data sent across the internet is broken up into small chunks called packets.

Packets are small chunks of data that are sent over a network.

Packets can contain any type of data, including text, images, sound, and video.

Each packet has a header containing information about the packet.

Imagine this as an envelope for a letter.

The data itself is called the payload, and that would be like the letter inside the envelope.

Along with other data, the packet header includes the source address, so where the packet has come from, the destination address, so where the packet is going to, the total number of packets in the message, and the sequence number of this particular packet.

So let's have a look at this example.

This is going to the device with the IP address, 142.

1.

58.

81.

It's being sent from the device with the IP address, 205.

9.

40.

3.

And it's packet number one of a total of five packets.

Each packet follows its own route through the internet, and not all packets from the same message will follow the same route.

Packets may arrive at the destination in any order.

The data is reassembled at the receiving end using the packet sequence numbers.

Time to check your understanding.

Which sentence is true? A, a web server asks a web browser for the data needed to display a website.

B, data is always broken down into eight packets before it is sent, or C, packets can arrive at the destination in any order? Pause the video here whilst you have a think.

That's right.

C is the correct answer.

Packets can arrive at the destination in any order.

Which of these would not be part of a packet's header? A, the destination address where the packet is going to.

B, the source address where the packet is coming from.

C, the data being transmitted, or D, the total number of packets.

Pause your video whilst you have a think.

That's right.

The data being transmitted would not be part of the packet's header.

This would be in the packet's payload.

Okay, let's move on to the first task of today's lesson.

Task A, Part 1.

This image is part of a webpage being sent via the internet.

Write down the steps needed to send the image data.

Pause your video here whilst you complete the activity.

How did you get on? <v ->Did you think about the steps?</v> Here's a sample answer.

First, the data needs to be broken down into chunks called packets.

So you can see here the image has been divided up into eight parts.

Each packet is given a header containing the sender and destination addresses, the total number of packets, and the number of this packet in the sequence.

And then the packets are sent across the network.

If you had any gaps in your response, maybe pause the video here and make some more notes.

Okay, for part two, I'd like you to number the order of steps needed to reconstruct the image at the receiving end.

So, you've got the step description, but these are in the incorrect order.

So we've got all packets have arrived at the destination.

This continues until the final packet has been read and the image has been reconstructed.

The recipient finds the first numbered packet and reads the data.

The recipient finds the next packet and reads the data.

Some packets have arrived at the destination.

Pause the video here whilst you complete the activity.

How did you get on? You're doing a great job so far, so well done.

Here you can see we've put the numbers in to show the order of the steps.

So the first thing that's going to happen is that some packets have arrived at the destination.

The next thing that's going to happen is that all the packets have arrived at the destination.

The recipient then finds the first number packet and reads the data.

The recipient then finds the next packet and reads the data, and so on.

And this continues until the final packet has been read and the image has been reconstructed.

Did you get the correct order? Remember to make any corrections if you need to.

Okay, we are now moving on to the second part of today's lesson, which is to describe how protocols secure communication.

Protocols are the rules computers use to transmit data across networks.

Protocols make it possible to request and send data in an agreed format.

HTTP stands for Hypertext Transfer Protocol, and you might have seen HTTP at the start when you've added in a web address into your web browser.

HTTP is a protocol that describes how a browser requests a webpage from a web server and how the server responds.

HTTPS stands for Hypertext Transfer Protocol Secure.

HTTPS works in exactly the same way as HTTP, except that the data sent between your browser and the website is also encrypted.

If you send data to a web server using the HTTP protocol, the data is not encrypted.

This means that attackers could intercept and see the data.

For example, if you are browsing the World Wide Web via a public WiFi network.

If you send data to a web server using the HTTPS protocol, then the data is encrypted and protected.

Attackers can still intercept and see the encrypted data, but only the person you sent it to can decrypt it to understand the message.

This means that the message is secure.

Time to check your understanding.

HTTP is, A, a protocol that is used for all data sent across the internet.

B, a set of rules for sending data to and from a web server.

Or C, a secure protocol that encrypts data sent to a web server.

Pause the video whilst you have a think.

That's right, B is the correct answer.

HTTP is a set of rules for sending data to and from a web server.

Data sent and received from web servers using HTTPS is secure because, A, the data is encrypted.

B, the data is broken down into packets.

Or C, attackers cannot intercept the data? Pause your video whilst you have a think.

Did you select A? Well done.

Data sent and received from web servers using HTTPS is secure because the data is encrypted.

Remember, it doesn't necessarily mean that attackers cannot intercept the data.

We are now going to move on to task B of today's lesson.

We've got some sentences here, and your task is to fill in the blanks.

Note that you do not need to use all of the words that are provided.

Pause your video here whilst you complete the activity.

How did you get on? You're doing a great job, so well done.

You are asked to fill in the blanks.

When your browser communicates with a web server, it uses a protocol, which is a set of agreed rules for communication.

Data sent using HTTP can be read by an attacker.

Information such as bank details should be sent using HTTPS so that it is encrypted and can only be read by the intended recipient.

Did you get all of those correct? If not, don't worry.

You can always pause the video here and make any corrections.

Time for part two.

Why do you think it's important to check that HTTPS is being used before you enter your personal information on a website? Pause the video here whilst you have a think and complete the activity.

Great work.

Here's a sample answer.

HTTPS is a secure protocol, so even if an attacker intercepts my personal information, they cannot read it, as this is encrypted.

This would mean that my personal information is not revealed to someone I don't know.

Was your response similar? Remember, you can always pause the video here and make any changes if you need to.

You have done a great job today, so well done.

Let's summarise what we have learned today.

Web servers hold the data for websites.

You can request the data using your web browser.

Data sent across the internet is broken down into packets.

A protocol is needed so that both computers know the format to send and receive information.

HTTP and HTTPS are protocols used to send webpage data.

Data sent by HTTPS is encrypted to keep it secure.

I hope you'll join me again soon, bye.