Introduction
A computer network connects multiple computers to share data and resources. This chapter covers network
classification by scale, physical layout (topology), and the internet's foundational protocols and
terminology.
Types of Networks by Geographic Scale
| Network | Full Form | Coverage |
|---|
| LAN | Local Area Network | Small area — a single building/office |
| MAN | Metropolitan Area Network | A city or large campus |
| WAN | Wide Area Network | Large geographic area — countries, continents (the Internet itself is the largest WAN) |
| PAN | Personal Area Network | Very short range — a single person's devices (e.g., Bluetooth connections) |
Network Topologies
| Topology | Layout | Key Feature |
|---|
| Bus | All devices connected to a single central cable | Simple, cheap, but one cable failure affects the whole network |
| Star | All devices connected to a central hub/switch | Easy to manage; central hub failure affects the entire network |
| Ring | Devices connected in a closed loop | Data travels in one direction around the ring |
| Mesh | Every device connected to every other device | Highly reliable (redundant paths) but expensive to set up |
| Hybrid | Combination of two or more topologies | Flexible, used in complex/large networks |
TCP/IP Model
Flowchart — TCP/IP Four-Layer Model
Application Layer — user-facing protocols (HTTP, FTP, SMTP)
↓
Transport Layer — end-to-end delivery (TCP, UDP)
↓
Internet Layer — addressing and routing (IP)
↓
Network Access Layer — physical transmission of data
| Protocol | Full Form | Use |
|---|
| HTTP/HTTPS | HyperText Transfer Protocol (Secure) | Web page transfer (HTTPS is encrypted) |
| FTP | File Transfer Protocol | Transferring files between computers |
| SMTP | Simple Mail Transfer Protocol | Sending emails |
| TCP | Transmission Control Protocol | Reliable, ordered data delivery |
| IP | Internet Protocol | Addressing and routing data packets |
| DNS | Domain Name System | Translates domain names (google.com) into IP addresses |
Key Internet Terminology
| Term | Meaning |
|---|
| IP Address | Unique numerical identifier for each device on a network |
| URL | Uniform Resource Locator — the address of a specific web resource |
| ISP | Internet Service Provider — company providing internet access |
| Modem | Converts digital signals to analog (and back) for data transmission over telephone lines |
| Router | Directs data packets between different networks |
| Bandwidth | The maximum data transfer rate of a network connection |
| Cookies | Small data files stored by websites in a browser to remember user preferences/sessions |
Wi-Fi and Bluetooth
| Technology | Range | Use |
|---|
| Wi-Fi | Medium range (up to ~100m) | Wireless local network internet access |
| Bluetooth | Short range (~10m) | Direct device-to-device connection (headphones, file transfer) |
✅ UPSC/SSC Focus: LAN/MAN/WAN/PAN scale distinctions · Five network topologies and their layout · TCP/IP four-layer model · Protocol-purpose matching (HTTP, FTP, SMTP, DNS) · IP address, URL, ISP terminology.