Spec & Goals 3 min
AQA Spec 3.5.1 — The internet, DNS, hosting and the cloud
By the end of this lesson you can:
- Explain that the internet is a worldwide network of networks.
- Describe how the DNS turns a domain name into an IP address.
- Define hosting and the cloud, with their advantages and disadvantages.
Warm-Up 5 min
You've met LANs and WANs. The biggest WAN of all is the internet. This lesson covers how it finds things and where websites and files actually live.
Quick starter
You type www.google.com, not a string of numbers. But computers route by numbers (IP addresses). What must happen first?
Reveal the idea
The name must be looked up and turned into an IP address. The system that does this is the DNS — the internet's phone book.
Key Concept — finding things online 14 min
The internet is a global network of interconnected computer networks. The World Wide Web is the collection of websites on the internet — they are not the same thing.
IP addresses and domain names
Every device on the internet has an IP address (e.g. 142.250.66.4). Humans prefer domain names (e.g. google.com). The job of mapping one to the other belongs to the DNS.
How a DNS lookup works
- You enter a URL; the browser asks a DNS server for that domain's IP address.
- If that server doesn't know it, it asks other DNS servers until the IP is found.
- The IP address is returned to your browser.
- The browser uses the IP address to request the web page from the correct web server.
Hosting and the cloud
Hosting means storing a website or files on a powerful, always-on server so others can access them over the internet. The cloud means using remote servers over the internet to store data or run software, instead of doing it on your own computer.
| The cloud — advantages | The cloud — disadvantages |
|---|---|
| Access files from any device, anywhere. | Needs an internet connection to use. |
| No need to buy/maintain your own servers. | Ongoing subscription cost; you rely on the provider. |
| Easy to share; automatic backups; scales up easily. | Security/privacy concerns — your data sits on someone else's servers. |
Worked Example — a DNS lookup, step by step 12 min
Problem: Priya types www.mschool.edu.my. Trace what happens before the page appears.
- Browser asks a DNS server: "what is the IP for
www.mschool.edu.my?" - DNS finds and returns the IP address (e.g.
203.0.113.5). - The browser sends an HTTP request to that web server for the page.
- The web server returns the page and the browser displays it.
Try It Yourself 12 min
Goal: State what the DNS does.
Goal: Describe the difference between the internet and the World Wide Web.
Goal: A startup is choosing between buying its own server and using cloud storage. Give two advantages and one disadvantage of the cloud option.
📝 Exam Practice 10 min
Define the term the internet.
Mark scheme
- A worldwide collection of interconnected (computer) networks (1).
Describe how the DNS is used when a user types a web address into a browser.
Mark scheme
- The browser sends the domain name to a DNS server (1).
- The DNS server looks up / returns the matching IP address (1).
- The browser uses the IP address to request the page from the web server (1).
Explain one advantage and one disadvantage of storing a school's files in the cloud.
Mark scheme
- Advantage — access from anywhere / automatic backups / no servers to maintain / scales easily (1).
- Disadvantage — needs internet access / ongoing cost / security & privacy of data held by a third party (1).
Recap & Key Terms 3 min
The internet is a worldwide network of networks; the web is the sites on it. The DNS translates domain names into IP addresses so browsers can find web servers. Hosting stores sites/files on remote servers, and the cloud lets you store data and run software on remote servers over the internet.
- The internet
- A worldwide collection of interconnected computer networks.
- DNS
- Domain Name System — translates a domain name into its IP address.
- Hosting
- Storing a website or files on a remote server so they can be accessed over the internet.
- The cloud
- Storing data and running software on remote servers accessed over the internet.
Homework 1 min
Task (≤ 15 min): Explain, in 4–5 sentences, what happens from typing www.example.com.my to the page appearing. Use the words DNS, IP address and web server.
Model answer
The browser sends the domain name to a DNS server. The DNS server looks up the matching IP address and returns it. The browser then uses that IP address to send a request to the correct web server. The web server sends back the web page, which the browser displays.
Award marks for: DNS lookup of the name (1); IP address returned (1); page requested from the web server using the IP (1).