Lesson video

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

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

In today's lesson, we're going to be exploring how addresses are used in networks and the role of IP addresses and domain name systems. Welcome to today's lesson from the unit Network Fundamentals.

This lesson is called Network Addressing, and by the end of today's lesson, you'll be able to explain how different types of network addressing are combined to enable devices to communicate on a network.

Shall we make a start? We will be exploring these key words throughout today's lesson.

Let's take a look at them now.

IP address.

IP address, a unique number assigned to each device on a network used to identify it and allow it to send or receive data.

DNS, domain name system.

DNS, domain name system, a hierarchy of servers that work together to resolve domain names to corresponding IP addresses.

Look out for these key words throughout today's lesson.

Today's lesson is split into two parts.

We'll start by explaining IP addresses and DHCP in networks, and then we'll move on to describe the DNS role in network addressing.

Let's make a start by explaining IP addresses and DHCP in networks.

Every single device that connects to the internet needs a unique address called an IP address.

An IP address is a series of numbers.

So here's an example, 192.

168.

1.

1.

An IP address works in a similar way to addresses for houses and buildings.

Each building has its own unique address that the postal service and delivery companies use to deliver mail to the correct recipient.

So here we've got an example, Sam Brown, 22 Townsend Road, Cumbria.

Every device on the internet has its own unique IP address.

When you request data through the internet, the request is made through your chosen internet service provider or ISP.

So you can see here we have a laptop with the IP address, 192.

168.

1.

1, and the request is going out to the ISP.

Your ISP connects you to billions of devices that are connected to the internet.

Each device has their own unique IP address.

So here we've got a network with of different nodes all with their own IP addresses.

Okay, time to check your understanding.

I have a true or false statement for you.

Your internet service provider, or ISP, is responsible for connecting your device to other devices on the internet.

Is this true or false? Pause the video whilst you have a think.

Did you say true? Well done.

When you request data through the internet, your ISP acts as the gateway connecting you to the vast network of billions of other devices.

A public IP address is assigned to your home network by your internet service provider.

A private IP address is used within your home network to identify individual devices like laptops, phones, and printers.

So here we've got an example of a home network with some private IP addresses.

So we have two smartphones, each with individual IP addresses and a laptop as well.

And then we have the router, which is obviously going to connect out to the internet.

All devices in your home share one public IP address when communicating on the internet.

Each device has a unique private IP address to communicate inside the local network.

So here we've got the router with the public IP, which in this case is 84.

92.

123.

17 which is going out to connect to the internet.

And then behind that router, we have our home network.

With the private IP addresses.

The dynamic host configuration protocol, DHCP, makes it easier for devices to join a network.

It is used to automatically assign an IP address to any device that joins a network.

This allows devices to join quickly without needing manual setup.

When a router connects to the internet, it sends a request for an IP address.

Your ISP uses DHCP to assign a public IP address to your router.

Your router then acts as a DHCP server for your local network.

Assigning private IP addresses to your devices.

So for example, phones, laptops, maybe tablets, et cetera.

DHCP is useful because it saves time compared to manual IP address assignment.

It reduces errors when managing large networks.

It frees up addresses when devices disconnect, and it makes it easy to connect new devices automatically.

Okay, time to check your understanding.

I have a question for you.

What is the primary purpose of the dynamic host configuration protocol, DHCP? Is it A, to manually set up network connections for devices; B, to secure data against cyber attacks; or C, to automatically assign IP addresses to devices when they join a network? Pause the video whilst you think about your answer.

Did you select C? Well done.

The DHCP automatically assigns IP addresses to devices when they join a network.

Okay, we're moving on to our first task of today's lesson, Task A.

For part one, I'd like you to explain what is an IP address and why does every device connecting to the internet need one.

For part two, describe how your home router uses DHCP when it connects to the internet.

And when your devices connect to your home network.

Pause the video whilst you complete the task.

How did you get on with the task? Did you manage to answer both of the questions? Well done.

Let's have a look at some sample answers together.

For part one, you were asked, what is an IP address and why does every device connecting to the internet need one? And IP address is a unique series of numbers such as 192.

168.

1.

1 assigned to every device that connects to the internet.

It functions like a postal address for houses, ensuring data is delivered to the correct recipient device.

For part two, you asked to describe how your home router uses DHCP when it connects to the internet and when your devices connect to your home network.

When your home router connects to the internet, your ISP uses DHCP to assign a public IP address to your router.

Your router then acts as a DHCP server for your local home network, automatically assigning private IP addresses to your devices like phones and laptops when they join.

Did you have this detail in your answer? Remember, if you need to pause the video and make any corrections, you can do that now.

Okay, so we've explained IP addresses and DHCP in networks.

Let's now move on to describe the DNS role in network addressing.

A domain name system, DNS, associates a website address with its IP address.

When you type raspberrypi.

org into your browser, the browser will perform a series of checks on that address.

First, it will check if you have visited the website before.

If you have, then your computer will already know the IP address.

If unsuccessful, it will use the DNS to find the IP address for the website.

The web browser establishes a connection with the server at the IP address specified by the DNS.

The server will then check what has been requested and start to build a response.

It will then send the HTML page and any other files like images to your computer.

Okay, time to check your understanding.

I have a true or false statement for you.

Typing a website address usually makes your browser immediately use DNS to find its IP address.

Is this true or false? Pause the video whilst you have a think.

It's false, but why is it false? Your browser first checks if you've visited the website before to see if it already knows the IP address.

It does this before it then goes out to use DNS if you haven't visited the site before.

A DNS server isn't just one single server.

There are thousands of DNS servers all around the world.

If your computer doesn't know the IP address for the website that you need, it will try and find that IP address in the fastest way possible.

First, it checks with your ISP's DNS server.

For example, an ISP may have two DNS servers that store the most commonly visited website IP addresses that their customers view.

If the website's IP address cannot be found here, then it checks the fastest available root DNS server.

The root DNS server is at the very top of the DNS server hierarchy.

It knows the location of all the DNS servers on the top level domain, which is sometimes called the TLD.

The top level domain contains IP addresses for specific domain name extensions such as.

com and.

uk.

If the computer is trying to access the IP address for a.

com URL, then it'll go to the.

com TLD server.

The.

com TLD server has a list of all the authoritative name servers, ANS.

ANS are the web servers that use a.

com extension.

For example, ww.

google.

com or www.

youtube.

com.

The authoritative name servers for Google tell your computer the IP address for google.

com.

Okay, time to check your understanding.

I have a question for you.

Which type of DNS server does your computer first typically check for a website's IP address? Is it A, a top level domain or TLD server; B, your internet service provider's DNS server; or an authoritative name server or ANS? Pause the video whilst you have a think.

Did you select B? Well done.

Your computer will first typically check your internet service provider's DNS server.

Okay, we are moving on to our next task of today's lesson, task B, and you've done a fantastic job so far, so well done.

Describe the journey a request takes through the different types of DNS servers.

So root, TLD and authoritative name servers to find a website's IP address if it's not found on your ISP server.

Pause the video whilst you have a go at the task.

How did you get on with the task? Did you manage to answer the question? Well done.

Let's have a look at sample answer together.

If a website's IP address isn't found on your ISP's DNS server, the request then goes up the hierarchy.

So firstly, it checks the fastest available root DNS server, which is at the very top of the DNS server hierarchy.

This server knows the location of all the DNS servers for top level domains such as.

com or.

uk.

The root DNS server directs the request to the correct TLD server.

For example, the.

com TLD server.

The TLD server has a list of all the authoritative name servers, ANS, for websites using that extension.

For example, all.

com websites, it directs the request to the correct ANS for the specific website.

Finally, the authoritative name server for that website, let's take the example of www.

google.

com, provides your computer with the specific IP address for the website, allowing your browser to establish a connection with the server.

Did you have all of those steps in your answer? It's quite a complicated process, so if you need to pause the video, maybe go back through a few slides, do that now.

Okay, we've come to the end of today's lesson, Network Addressing, and you've done a fantastic job, so well done.

Let's summarise what we've learned in this lesson.

An IP address is a unique number that identifies each device on a network.

DHCP, dynamic host configuration protocol, automatically assigns IP addresses to devices.

DNS, or domain name system, matches website names to their IP addresses so devices can connect over the internet.

I hope you've enjoyed today's lesson, and I hope you'll join me again soon.

Bye.