What happens when you open a website?
You type a web address and press Enter. Many small steps happen in less than a second.
Your phone gets an address. It finds the server. It asks for the page. The page comes back safely. Each step has its own rules. A protocol is a set of rules that computers follow to talk to each other.
Key words
| Word | What it means | Example |
|---|---|---|
| IP address | A number that names a device on a network. | 10.0.10.1 |
| Encryption | Scrambling data so that only the right people can read it. | HTTPS |
| Network | Computers joined together to share data. | The college network |
| Packet | A small piece of data sent over a network, with an address on it. | One part of a photo |
| Router | A device that joins networks and sends data the right way. | A home router |
| Port | A number that says which program on a computer should get the data. | 443 for HTTPS |
The cells students fill in are left blank in this preview.
More key words
| Word | What it means | Example |
|---|---|---|
| Protocol | A set of rules that computers follow to talk to each other. | HTTP |
| HTTP | Hypertext transfer protocol. It asks for web pages and sends them back. | Loading a page |
| HTTPS | HTTP with encryption. It keeps the page and your data private. | The padlock in the browser |
| SMTP | Simple mail transfer protocol. It sends email. | Pressing Send |
| POP | Post office protocol. It downloads email to one device. | Mail on one laptop |
| IMAP | Internet message access protocol. It keeps email on the server, so every device sees the same mail. | Phone and laptop show the same mail |
| RIP | Routing information protocol. Routers share how many steps it takes to reach each network. | Small networks |
| OSPF | Open shortest path first. Routers share a map and find the best path. | Larger networks |
| FTP | File transfer protocol. It moves files between computers. | Uploading a website |
| SFTP | Secure file transfer protocol. It moves files with encryption. | A safer upload |
| DHCP | Dynamic host configuration protocol. It gives a device an IP address. | Joining the Wi-Fi |
| DNS | Domain name system. It turns a name into an IP address. | example.com to a number |
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The protocols at a glance
| Group | Protocol | Job |
|---|---|---|
| Web | HTTP | Web pages |
| Web | HTTPS | Web pages, encrypted |
| SMTP | Sending email | |
| POP | Download email | |
| IMAP | Read email on the server | |
| Routing | RIP, OSPF | Routers share routes |
| Application | FTP | Files, not encrypted |
| Application | SFTP | Files, encrypted |
| Application | DHCP | Gives IP addresses |
| Application | DNS | Names to IP addresses |
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Extra: Port numbers
| Protocol | Usual port |
|---|---|
| HTTP | 80 |
| HTTPS | 443 |
| SMTP | 25 or 587 |
| POP | 110 |
| IMAP | 143 |
| FTP | 21 |
| SFTP | 22 |
| DHCP | 67 and 68 |
| DNS | 53 |
| RIP, OSPF | Used between routers |
The cells students fill in are left blank in this preview.
Quick check: which protocol?
Have a go
Quick check: which protocol?
5 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Web protocols
HTTP is how a browser asks a web server for a page. The server sends the page back. But HTTP is not private. Anyone between you and the server can read it.
HTTPS is HTTP with encryption. It scrambles the data so only you and the server can read it. Use it for logins and payments. Look for the padlock.
Mail protocols
SMTP sends email: from your device to your mail server, and from server to server.
To read email, you use POP or IMAP. POP downloads the mail to one device and often removes it from the server. IMAP leaves the mail on the server, so your phone and your laptop show the same inbox.