Types of networks: PAN, LAN, MAN, WAN
| Type | Area | Example |
|---|---|---|
| PAN (Personal Area Network) | about 10 m around one person | phone + earbuds by Bluetooth, laptop + phone hotspot |
| LAN (Local Area Network) | a room, building or campus (up to about 1 km) | school computer lab, office network |
| MAN (Metropolitan Area Network) | a city or town (up to about 50 km) | city cable TV network, a bank's branches in one city |
| WAN (Wide Area Network) | countries or continents | the Internet, a railway booking network |
As size grows, speed usually falls, cost rises, and ownership moves from one person or group to many companies. LANs are fast and privately owned; WANs join many LANs and MANs.
Network topologies: bus, star, tree
A topology is the arrangement (layout) of computers and cables in a network.
Bus topology
All nodes connect to one main cable called the backbone, with a terminator at each end to stop signals bouncing back. Data travels along the bus and every node sees it.
- Good: least cable, cheap, easy to add a node.
- Bad: a break in the backbone stops the whole network; hard to find faults; slows down with many nodes.
Star topology
Every node has its own cable to a central device (hub or switch).
- Good: one cable failure affects only that node; easy to add or remove nodes; easy to find faults.
- Bad: more cable; if the central device fails, the whole network stops.
Tree topology
A hierarchy (levels) of star networks joined to a root, like a tree with branches; it mixes bus and star ideas.
- Good: easy to expand level by level; suits large buildings and campuses; faults can be isolated to one branch.
- Bad: needs lots of cable; if the root or a main branch fails, everything under it is cut off.
Network protocols
A protocol is a set of rules for how devices format, send, receive and check data.
- TCP/IP (Transmission Control Protocol / Internet Protocol): the base of the Internet. TCP breaks a message into packets, numbers them, checks they all arrive and puts them back in order. IP puts the address on each packet and routes it.
- HTTP (HyperText Transfer Protocol): rules for a browser to ask a web server for pages and for the server to reply.
- HTTPS (HTTP Secure): HTTP with encryption, so passwords and payments cannot be read on the way. Look for the padlock.
- FTP (File Transfer Protocol): uploads and downloads files between computers.
- SMTP (Simple Mail Transfer Protocol): sends email from your mail app to the mail server and between servers.
- POP3 (Post Office Protocol 3): downloads email from the server to your device (usually removing it from the server).
- PPP (Point-to-Point Protocol): links two devices directly, such as a computer and an ISP over a phone line; it handles login and error checks.
- TELNET: lets you log in to a remote computer and type commands on it as if you were there (text only, not secure; SSH is the safe version).
- VoIP (Voice over Internet Protocol): turns voice into digital packets and sends them over the Internet, as in WhatsApp or Meet calls.
Try it: map your school network
Visit your computer lab. Follow the cables from each computer. Do they all go to one switch box (star)? Are there several switches joined to one main switch (tree)? Draw what you find. Then list the network types you use in a day: earbuds (PAN), lab (LAN), city Wi-Fi or cable (MAN), Internet (WAN). In the 3D free-play step, cut a cable in each topology to see what fails.
Key formulas and definitions
- PAN < LAN < MAN < WAN (area)
- Bus: one backbone · Star: central hub/switch · Tree: stars in levels
- SMTP sends mail · POP3 downloads mail · HTTP/HTTPS web pages · FTP files · VoIP voice
- TCP: split, number, check, reorder · IP: address and route
Worked examples
1. Classify: (a) a smartwatch linked to a phone (b) 40 computers in a school building (c) a bank's ATMs across one city (d) offices of a company in Delhi and London.
(a) PAN (b) LAN (c) MAN (d) WAN.
2. In a bus network of 6 computers, the backbone cable is cut in the middle. What happens? What would happen in a star network if one computer's cable was cut?
Bus: the whole network stops working (signals bounce back and there is no path). Star: only that one computer loses connection; the others keep working.
3. A school has 4 blocks, each with a lab. Suggest a topology.
Tree (or star in each block joined to a central switch): each lab is a star around its switch, and the block switches join a main switch in the server room. It is easy to expand and a fault stays in one block.
4. Which protocol is used: (a) to send an email (b) to download email to your phone (c) to open a bank website safely (d) to upload a website's files to a server?
(a) SMTP (b) POP3 (c) HTTPS (d) FTP.
5. Explain the roles of TCP and IP when you download a photo.
TCP on the server cuts the photo into numbered packets and, on your device, checks every packet arrived and puts them in order (asking again for lost ones). IP puts your device's address on each packet and routers use it to forward the packets.
6. Why is HTTPS preferred over HTTP for login pages?
HTTPS encrypts data between the browser and server, so a password cannot be read by someone watching the network. HTTP sends it as plain text.
Common mistakes
- Saying POP3 sends mail. SMTP sends; POP3 receives (downloads).
- Thinking a star network stops when one cable breaks; only that node stops (the centre is the weak point).
- Mixing up MAN and WAN: MAN is a city, WAN is countries or the world.
- Treating TCP and IP as one job: TCP handles packets and reliability, IP handles addressing and routing.