4 – Packets and Routers

• Understand what the what a computer network is
• Explore different types of computer networks
• Discover what a router is and how it connect devices together
• Understand what packets are and how we use them to transfer data

• network
• communication

• router
• packets

• header
• topology

• Open a new Word file and write down a definition of what you think a computer network is at the moment.

• A Computer Network is when we connect two or more computers together so they can communicate with each other.
• There are many different types of network, with names like mesh, bus and ring.
• The star network topology is the type you will have used the most, it is also the type used here at school.
• Your computer is connected by copper ethernet cables to a central server elsewhere in the school.

• The video below will give you an overview of how a network works:

• Having watched the video, try and produce a summary of it for your notes.

• The image here shows the devices that might make up a home network.
• Save the image by right clicking on it, and then open it up in PowerPoint.
• Then label the devices using the list below.
  • Desktop Computer
  • Smartphone
  • Router
  • Smart TV
  • Games Console
  • Laptop

Ethernet Cables

• We can connect up devices on a network using cables called ethernet cables. You’ve probably got one coming out of the back of the computer you are using right now.
• Ethernet cables are plugged into ethernet ports on devices.

• On your diagram, draw on lines that link the the ethernet ports on the Desktop Computer, Smart TV and Games Console to the Router.
• Think about why these devices should be connected by cables and not wirelessly.

Wi-Fi

• Some devices connect wirelessly. Wi-Fi stands for Wireless Fidelity.
• Wi-Fi uses radio waves to allow devices to communicate with each other.
• On your diagram, add in a Wi-Fi icon to indicate that the Router is able to connect to the Smartphone and Laptop using WiFi.

Other Connection Technologies

• Devices can connect with each other using a few other methods. Use the Web to try and answer the following questions:
  • What is Bluetooth?
  • What is the range of Bluetooth communications?
  • What are Fibre Optic cables?
  • What does 5G mean?

Your diagram should probably look something like this now:

• Let’s imagine that the desktop computer is going to send an image file to the laptop.
• The image is called tree.jpg and has a size of 1.5MB (That’s 1.5 Million bytes).

• 1.5 Million bytes is too large to send in one go, so the Desktop Computer needs to break up the file into small chunks called packets.
• Each packet has an average size of about 1.5KB (That’s 1500 bytes).
• The Desktop Computer breaks up the image into packets, and adds some extra data onto the packet as well.

• Each packet is then sent to the router.
• When the router receives a packet, it looks at the receiver’s IP Address, and then sends the packet onto the correct device on the network.
• The receiving device (in this case the laptop) receives all these packets, and uses the packet number to assemble them all in the correct order.
• Sometimes a packet get’s lost or destroyed on the way. The receiving device will know that a packet is missing, and can use the sender’s IP address to ask for the packet to be sent again.

• Imagine you had to try and explain how an image is sent over a network, from one device to another.
• Create a presentation using PowerPoint, and the image you drew earlier of a network, to explain how a file is sent over a network.
• Your teacher will award you a silver, gold or platinum badge, depending on the clarity of your presentation.

In this lesson, you…

• Explored how a network works including different types of network.
• Looked at routers and packets and how they are used to transport data on a network.

Next lesson, you will…

• Use Scratch to model a network including how packets move around a network.
• Use our DNS model from last lesson to include it in our network.

• Presentation shows some information on how a file is sent over a network.

• Presentation shows clearly how a file is sent over a network.

• Presentation shows clearly how a file is sent over a network with extra detail and information.