What is a Protocol?
🎬 Watch the 10:53 video of this chapter ↓On a road, everyone drives on the left and stops at a red light. Nobody argues about it each time. Those shared rules are what let thousands of strangers use one road safely. Computers on a network need the same thing.
1What a protocol is
You met the protocol already as one of the five components of data communication. There, a message sent without a shared protocol arrived as nonsense. A protocol decides things like:
- how devices on the network identify one another (by address);
- what form the data is put into for the journey;
- whether data that arrives is for this device or should be passed on;
- how to check that all the data arrived, with nothing lost;
- how to put the pieces back in order at the other end.
2Why networks need protocols
The sender and receiver may be on different networks, in different places, working at different speeds. Your NCERT book gives three reasons protocols are needed: flow control, access control and addressing.
Flow control: a fast sender, a slow receiver
Computer A sends data at 1024 Mbps. Computer B can take it in at only 512 Mbps. Without a rule, B cannot keep up and data is lost. With flow control, B can tell A to slow down.
Send with no rule, then turn flow control on and send again. Drag sideways to turn.
A teaching model: two packets a moment from A, one a moment into B, room for three to wait. Real flow control is the same idea with far bigger numbers.
Access control: two computers, one cable
When several computers share one link, they must not all send at the same instant. If they do, the signals collide and the data is damaged. Access control decides who may use the link, and when.
Send with no rule, then with the turn-taking rule. Drag sideways to turn.
Addressing
Every device needs an address, so that data reaches the right one. You have seen this rule at work already: the IP address, set by the Internet Protocol.
Think of a phone call
3The nine protocols in your syllabus
Each protocol is a set of rules for one job. The rest of this chapter takes them one at a time.
| Protocol | Full form | Its job |
|---|---|---|
| 📦 TCP/IP | Transmission Control Protocol / Internet Protocol | cuts data into packets, addresses and delivers them |
| ↔️ PPP | Point to Point Protocol | a direct link between two devices |
| 🌐 HTTP | HyperText Transfer Protocol | fetches web pages |
| 🔒 HTTPS | HyperText Transfer Protocol Secure | fetches web pages, encrypted |
| 📁 FTP | File Transfer Protocol | transfers files |
| 📤 SMTP | Simple Mail Transfer Protocol | sends email |
| 📥 POP3 | Post Office Protocol version 3 | retrieves email from the mail server |
| 📞 VoIP | Voice over Internet Protocol | voice and video calls over the Internet |
| ⌨️ TELNET | Teletype Network | logs in to a remote computer |
4From the board papers
▶Show the answer
Protocol.
▶Show the answer
Devices on a network may work at different speeds and share the same links. Protocols give them common rules for flow control (a fast sender must not flood a slow receiver), access control (who may use a shared link, so data does not collide) and addressing (data reaches the right device), so that communication is successful and reliable.
▶Show the answer
A protocol is a set of standard rules that the sender, the receiver and all intermediate devices follow to communicate over a network. Example: HTTP, the protocol for web pages.
5Check yourself
Who has to follow a network protocol?
A sender is faster than its receiver, and data is being lost. Which need of protocols does this show?
Network Protocols, in 10:53
One animated video of the whole chapter, narrated. Watch it before the lessons for the big picture, or after them to revise.