Recap the last lessons. We've learned about what a network is, how the internet is a network of networks and how everything is converted into binary data so it can be sent between devices across the Internet but ...

 

How does our data know where to go?

It knows where to go as it’s all sent to an IP (Internet Protocol) address. Every device, server and website online has a unique IP address, so the data knows where to go.

What’s our IP address at school right now? You can find out by going to Yougetsignal.com!

 

Some networks give every device a permanent IP address, others use a dynamic system, which means each time the device connects to the network it is assigned an IP address from a list available to that network at that time.

 

An IP address is made up of numbers and is a bit like a phone number or street address. Traditional IP addresses are represented by 32 bits.

 

 

Each part of the number identifies each of the networks that lead to the device, then the actual device itself within the final network. It’s a bit like a postal address, each line adds information.

 

 

Even though this system provided 4 billion possible IP addresses, it’s not enough! This 32 bit system for IP address is called IPv4 and was designed back in 1973. But there are now so many online devices that we are running out of unique IP addresses. To solve this problem, a new system is already being introduced, called IPv6 which uses 128 bits instead of 32. 

e.g.

3FFE:F200:0234:AB00:0123:4567:8901:ABCD

 

This new system will provide 340 undecillion unique addresses!

340,000,000,000,000,000,000,000,000,000,000,000,000

That's a lot!

 

How data travels

So we know how the data knows where to go, but what is its actual journey like? And how does it get their reliably?

Show this video from Code.org:

 

 

Packets

Data that needs to be sent over a network is split up into small chunks called packets. The transmitting computer adds extra information to each packet, including its: source address, destination address and packet number (so packets can be reassembled in the correct order). Time to live ensures that any packets that get stuck in the Internet eventually expire, so the network doesn’t get clogged up. 

 

 

Routers

On the Internet, devices called routers identify the destination each packet of data is being sent to and choose the best route to send the packet down to get it closer to its destination. A set of packets may be routed along different paths if there is congestion or if a router breaks. 

 

 

Sending your own packet data

Put each child with a partner, but do not sit them together. Their partner should be someone sitting on another table.

Give every child a copy of the Sending data in packets worksheet and ask them to complete the activity using the instructions.

1. Draw any picture over the top of the grid.
2. Complete the packet data on each packet square. The Destination = person’s name you are sending it to (This would be an IP address in reality). The Source = your name (This would also be an IP address in reality).
3. Cut out each packet square
4. Place all your packets on the ‘router table’ - This should be a central table (or just a space on the floor) where all the children deposit their packets. It's fine for them to get mixed up, in fact, that's kind of the point!
5. Once all the packets have been handed in, distribute them amongs the class. They are all now going to become ‘Routers’. They will read the packet information and deliver it to the correct destination (person).
6. Once all the packets have been delivered, each person can put the packets they receive back together in the right order using the packet data, as a device would.

 

The Internet - A network of networks

Finally, give each child a copy of The Internet - A network of networks worksheet. It gives an illustration of the Earth, showing web servers of major companies, routers, internet service providers, homes, businesses and schools.

 

 

There are three tasks for the children to complete:

1. Connect all the routers and satellites to adjacent routers to show how the Internet connects the planet.
2. Draw a typical home network. Consider what kinds of devices it would include, ensure it has a router that connect the home to an internet service provider. 
3. On the back of the sheet, explain what happens when a user in the UK visits a website that is hosted on a webserver in the USA. Key words are provided to support them with their explanation: packets, routers, internet service provider, data, binary code, cables, satellites, wireless, web server.

 

The world’s submarine Internet cables

By completing the sheet, they should appreciate how countries have to be connected to one another for the Internet to work. So to finish, take a look at the video below that explains how all the major undersea Internet cables in the world are laid and the challenges they face.

 

 

Plenary

Assess the student understanding by asking the class

• What is an IP address? 
• What job to routers do?
• Why is internet data split into packets?