9 min readConcept sheetOften a 5- or 10-mark answer

Network equipment, client-server and advantages of networks

Hubs, switches, routers and gateways connect devices and networks; client-server networks let many users share data, devices and the internet.

HubRepeats data to every port

SwitchSends data only to the right device

RouterJoins networks and picks the route

GatewayJoins networks that use different protocols

Basic data communication equipment

Device	What it does	Where you see it
Network interface card (NIC)	Connects one computer to a network; has a unique MAC address	Inside every PC, laptop and phone
Modem	Modulates and demodulates: changes digital data into signals the line can carry, and back	The broadband box supplied by the ISP
Hub	Receives data and repeats it to every port	Old or very small LANs
Switch	Learns which device is on each port and sends data only there	The centre of an office star LAN
Repeater	Boosts a weak signal so it travels further	Long cable runs, Wi-Fi extenders
Bridge	Joins two LAN segments of the same type	Linking two parts of an office network
Router	Joins different networks and chooses the best path for each packet	Connecting the office LAN to the internet
Gateway	Joins networks that use different protocols, translating between them	Linking a LAN to a different kind of system
Wireless access point	Lets Wi-Fi devices join a wired LAN	Office and campus Wi-Fi

Hub vs switch

HubSends every message to every port. Cheap, but it wastes bandwidth and is less secure.

SwitchSends each message only to the port of the intended device. Faster and more secure; the standard in offices today.

The client-server model

back to Client sends a request

Clients are PCs or phone apps. Servers are powerful computers that store shared data (file, database, web, email servers).

Client-server vs peer-to-peer

Client-serverA central server stores data and controls security; clients request services. Easier backup and control, but the server costs more and is a single point of failure.

Peer-to-peerAll computers are equal and share files directly. Cheap and simple for a few PCs, but security and backup are weak.

Advantages of computer networks

Share hardware: one printer or scanner for many users.
Share data: one customer database used by all departments.
Share software and one internet connection.
Communicate quickly: email, chat, video meetings.
Central backup and security from the server.
Lower costs, e.g. network software licences.
Remote access: staff can work from branches or home.

In Sri Lankan business

When you check your balance on a Sri Lankan banking app, your phone is the client and the bank's server looks up your account and sends the answer back. At home, the router supplied by SLT-Mobitel or Dialog joins your Wi-Fi LAN to the internet.

Exam angle

Short answer: “Distinguish between a hub and a switch.” A hub repeats data to all ports; a switch sends data only to the port of the intended device, so it is faster and more secure.

Structured question: “Explain the client-server model with an example.” Clients send requests, a central server processes them and sends responses. Example: a banking app (client) and the bank's server.

Essay: “Discuss the advantages of computer networks to a business organisation.” Define a network, then explain sharing hardware, data and software, communication, central backup and security, cost savings and remote access, with a note on risks.

Remember it

Hub shouts to all; switch whispers to one; router finds the road; gateway translates.