Lesson video

Hello, my name is Mrs. Antrobus.

I'm so pleased you joined us for the lesson today.

Today, we're going to be learning about data packets.

Welcome to today's lesson from the unit, "Communication and the Internet".

Today's lesson is called, "Data Packets", and by the end of this lesson, you'll be able to explain how data is transferred across the internet.

During today's lesson, we'll be using these keywords.

Let's go through them together now.

Packet, packet.

Small chunks of a whole file that are sent or transmitted over a network.

Each packet contains a header and a payload.

Header, header.

Part of a packet that contains addressing and other data.

Network, network.

A group of connected computers.

Payload.

Payload.

Part of a packet that contains the message being sent.

Today's lesson will be broken down into two parts.

The first part, we will identify what makes up a data packet and in the second part of the lesson, we will describe how packets move across networks.

Let's get started.

A packet is a small piece of data sent across a network.

Izzy says, "It's like sending lots of small parcels instead of one big box." That's correct, it is, Izzy.

Izzy asks, "Why split a file into packets?" Well, large files are split into packets so they can be sent more reliably and if part is lost, only the missing packets need to be resent rather than the entire file.

Does that make sense? If you think about sending an image file for example, then that can contain thousands of packets, so it makes sense when you think of it like that.

There are two main parts to a data packet, a header is information about the sender, receiver, packet order and the total number of packets.

A data payload is the part of the file being sent, so the main message or the main piece of data.

Let's check your understanding.

True or false? The header contains the message being sent.

Is that true or false? Pause the video and give the statement some thought.

Okay, what do you think? Is that statement true or false? Well, if you said false, that would be the correct answer, but why is that? While the header contains key information, the payload holds the message or the data.

A short message could be sent by splitting it into multiple packets.

Here we have packet one, which contains hello, packet two contains how and packet three contains are you.

Each packet needs a header to say what part it is.

Packets are numbered so the receiving computer can put them back together in the correct order.

Here we have the short sentence.

The first packet is hello, packet two, how and packet three, are you.

Without the packets being numbered, the computer wouldn't put them back in the correct order so the sentence wouldn't make sense.

And imagine if this was packets for a much larger file with lots of pieces of data.

It's really important that packets are numbered, so the data and the messages that are being sent across the network makes sense.

Let's check your understanding.

Which part of the packet directs the computer where to send it? Is it A, the payload, B, image, C, header or D, video? Pause the video for a moment and consider your answer.

Okay, how did you get on with that question? Well, if you put C, you will be correct.

Well done.

Do you remember from the beginning of the video, we talked about how the header contains sender information, receiver information, the order of the packets and also the total number of packets? You're doing really well in this lesson.

Let's move on to task A.

Okay, in this task, we're now going to see what we've learned from the beginning of the lesson.

You're going to answer the following questions.

Question one.

Why do we break data into packets? Question two.

What happens if a packet is missing or mixed up? Question three.

How does the computer know the right order? Okay, you're going to pause the video now and give these three questions some thought.

Welcome back.

How did you find those three questions? Were they easy or did you find them a little bit tricky? Let's have a look at some responses together.

Question one.

Why do we break data into packets? We break data into packets, because it is easier and more reliable to send smaller parts.

Remember, images have large file sizes and can have thousands of packets, so it's really important that those file sizes are broken down into small packets so it's more reliable and easy to send them across the network.

Okay, let's compare your answer to the answer we have here.

The question was, "What happens if a packet is missing?" The receiving computer will request or ask the sending computer to send the missing packet again.

Remember that the header information tells the computer how many packets there should be and each one is numbered so the packet can be requested.

Let's now have a look at question three.

How does the computer know the right order? It looks at the number on each packet.

The header says which number packet it is and how many packets there are in total.

Remember, the header information provides the computer with the number of packets that should be received and what order they should be in, so the computer can use that to check against.

How did you get on with those questions? Were you able to remember why files are broken down into packets, what happens if there's a missing packet and how the computer knows to put it in the right order? If you did, well done.

If not, don't worry.

The questions were a little bit tricky.

You could go back and have a look at the content we've learned so far and have another go at the questions.

We're now going to move on to the second part of our lesson.

Describe how packets move across networks.

Lucas says, "What is a network?" Well, a network is a group of connected computers that can send data to each other.

Think about your home or in your school.

You may have seen networks in a classroom.

You might even have a computer suite where there's lots of computers that are all connected together or at home, you may have a laptop that connects to your printer or you may be able to connect your handheld device, such as a tablet or smartphone to a router so that you can connect to the internet.

That is basically what a network is.

A number of devices connected together to share peripherals, which are things like printers and share access to the internet.

Lucas asks, "How do packets move?" Packets are sent from router to router until they reach the right address.

Different packets may travel through different routes.

Data is sent in packets over both the internet and smaller internal networks.

There are many different routes through networks.

For example here, Izzy may be sending a message to Sam.

So Izzy is the sender and Sam is the receiver.

And each of these circles with numbers in represent a router.

Now, the message could take a number of different ways to get from Izzy to Sam.

Let's have a look at that in a bit more detail.

Not all packets take the same route.

For example, packet one goes through routers one, four, and seven.

Packet two might go through routers two, five and eight and packet three goes through routers three, six and nine.

They all take different paths, but end up in the same place.

Does that make sense? Jun says, "What ensures that packets get to the right place?" Well, the packet header, remember it identifies or states or says the destination for the data.

It includes the sender's IP address, the receiver's IP address, the packet number and the total number of packets.

This information tells routers where to send the packet.

Let's check your understanding.

The packet number tells routers where to send the packet.

Is that true or false? Pause the video and give that statement some thought.

Okay, what was your response? Well, if you said false, you will be correct, but why is that? The IP address is used to identify where the packet is being sent.

The packet number are the individual numbers that are assigned to each packet within a file, for example, packet one, packet two, packet three and so on.

When all packets arrive at the destination, the device reassembles them using the packet numbers in the header.

Here we have an example on the left of how the packets might arrive.

Packet three arrives first.

The content of packet three is the word packets.

Packet one arrives next.

The content of packet one is data is.

And finally, packet two arrives and the contents of packet two is transferred in.

Now, in that order, that data doesn't make sense.

So this is where the computer rearranges the packets into the correct order, and that's why we need packet numbers.

So packet one, data is, packet two, transferred in packet three, packets.

So now the packets are in the correct order and the message is easy to read and makes sense.

It says, "Data is transferred in packets." Does that make sense to you? Let's have a look at the next slide.

Lucas asks, "What happens if something goes wrong?" Well, if a packet is missing, the receiver asks for it again.

This ensures the full message is received and remember, the head of information tells the receiver how many packets they are expecting.

So if they're expecting 10 packets and they only receive nine, then the receiver knows that he needs to ask for the remaining packet for the message to make full sense.

Let's check your understanding.

Why is it important that the packets are numbered? A, so the colours are brighter, B, so they can be sent faster, C, so they can be put back together in the right order and D, so the header is shorter.

Give that question some thought.

Pause the video.

Okay, how did you get on? What response did you pick? If you picked C, you will be correct.

Well done.

You were able to remember that the packets are numbered so that they could be put back together in the right order.

Remember our jumbled up message earlier? This is why packets are numbered so that they become sorted and make sense.

Well done, you're doing really great so far.

What types of data can be sent in packets? Well, images can be sent in packets.

So when you take a photograph with your smartphone or tablet and then you send it to somebody, that uses data packets.

The same applies to videos.

Maybe you're watching a video, so that data is coming to your device through packets.

Audio files are the same.

If you're listening to music on a device or you send an audio file to somebody else, a voice recording, that will use packets.

Files, such as documents, Word files, spreadsheet files will all be sent using packets.

Even text files, just a basic text file is sent using a packet.

All of these are broken into packets to be sent.

We're now going to have a look at task B.

You're going to order the packet journey.

We have a table here with the steps of the journey on the left-hand side and then you are going to number the steps on the right-hand side.

Let's have a look at the steps of the journey together.

Each packet is given a header.

The device reassembles the message.

The message is split into packets.

Packets arrive out of order.

Packets are sent across a network.

What you're going to do now is pause the video and have a go at putting these steps into the correct order by putting a number next to them in the order that they should be.

Hope that makes sense, have a go at the task.

Okay, how did you get on? Did you find that easy or was it a little bit tricky? Let's have a look at the solution together.

Okay, you can see the numbers here, so let's start with number one.

The first part of the packet journey.

Number one, the message is split into packets.

Number two, each packet is given a header.

Number three, packets are sent across a network.

Number four, packets arrive out of order and number five, the device reassembles the message.

How did you get on? Did you get the steps of the journey in the correct order? Well done if you did.

If not, don't worry.

You can go back over some of the content of the lesson and have another go.

We have come to the end of today's lesson.

You have done a fantastic job.

Well done.

Let's summarise what we have learned.

Data packets are made up of headers and payload.

The headers contain the information about the message and the payload contains the message.

Everything sent over the internet, such as videos, images or text is broken into packets.

These packets are sent across a network.

Headers are used to show a packet's destination.

Once all the packets have been received, they are put back together to make a full message.

Thank you for joining in today's lesson.

I hope you enjoyed it and I look forward to seeing you next time.