Protocols are a set of rules for how computers communicate.
They stipulate:
- How communication starts
- How communication ends
- How the sent data is organized
- What to do when there’s an error
- How to resend data if there’s an error
Without protocols computers could receive data but wouldn't know what to do with it. If all computers follow the protocols communication should work with few issues.
There are thousands of protocols which manage different types of digital communication between devices, however the commonly used ones are:
- HTTP: Used by web browsers and web servers to manage website requests and sending web pages and connected resources in response to the requests.
- HTTPS: This has the same purpose as HTTP but uses encryption to protect the contents of the request and any data sent in response.
- POP: Is used for receiving mail from an mail server. It downloads all the messages on the server and then deletes them off the server. POP is an old protocol and was beneficial when server storage space was costly.
- IMAP: Is used for receiving mail from a mail server. It synchronizes mail between multiple devices and the mail server. The devices and mail server contain copies of the same data.
- SMTP: Used to send from a computer to the mail server or between mail servers.
- FTP: Used for transferring files from a computer / client to a server. Sometimes files can be transferred between clients / computers.
- IP: Responsible for how the packets move between networks (managed by routers). Uses IP addresses to identify the sender and destination.
- TCP: Responsible for splitting data into packets, re-ordering packets when received and ensuring all packets are received.
- Ethernet: Manages how data is physically transmitted down a cable.
