Networking Basics

Introduction

This unit's last stretch of the course moves from databases to how computers actually connect to each other — starting with what a network is, sorted by how far it physically reaches.

Concept

A computer network is a collection of interconnected devices able to exchange data with each other. Networks are classified by geographic scale:

• LAN (Local Area Network) — confined to one building or a small campus, like one school or office.
• MAN (Metropolitan Area Network) — spans a city or a large town, larger than a LAN, smaller than a WAN.
• WAN (Wide Area Network) — spans a large geographic area, potentially an entire country or the whole world. The Internet is the largest WAN in existence.

Explanation

This scale is really a spectrum, not three sharply separate categories — a school's own network is a LAN, several of a city's schools linked together could form a MAN, and connecting networks across many cities and countries is exactly how a WAN, and ultimately the Internet itself, is built: each larger category is made of many smaller networks joined together, not a fundamentally different technology.

Note: The Internet is not a separate fourth category — it's the standard example CBSE uses specifically to illustrate what a WAN actually is at its largest possible scale.

Summary

A network is a collection of interconnected devices exchanging data. LAN, MAN, and WAN classify networks by geographic scale — building/campus, city, and country/global — each larger category built from smaller networks joined together, with the Internet as the largest WAN of all.

Introduction

A network's devices need physical hardware to actually connect and direct traffic between them — this topic names the core pieces.

Concept

• Modem — converts digital data from a computer into a form that can travel over a telephone/cable line (and back), connecting a local network to an external one, like the Internet.
• Hub — connects multiple devices in a LAN, but simply broadcasts incoming data to every connected device, regardless of which one it's actually meant for.
• Switch — connects multiple devices in a LAN like a hub, but intelligently sends data only to the specific device it's addressed to.
• Router — connects different networks together (like a home LAN to the wider Internet), and directs data along the correct path between them.

Explanation

Hub versus Switch is the clearest, most exam-tested distinction here: both physically connect several devices, but a Hub wastes bandwidth broadcasting every message to everyone, while a Switch reads each message's intended destination and sends it only there — the same "targeted versus broadcast" idea, at the hardware level, that made WHERE so essential back in your SQL work.

Note: A Router connects networks to each other; a Switch connects devices within one network. Confusing the two is a common mistake — remember Router as the device that lets your home network reach the Internet at all.

Summary

A Modem connects a local network to an external line. A Hub broadcasts to every connected device; a Switch sends data only to its intended device. A Router connects separate networks together and directs data between them.

Introduction

Beyond the devices themselves, a network has a physical or logical shape — how its devices are actually arranged and connected. This topic covers the four standard layouts.

Concept

• Star Topology — every device connects individually to one central device (like a Switch). If one device's own cable fails, only that device is affected; if the central device fails, the whole network goes down.
• Bus Topology — every device connects to one single shared central cable (the "bus"). Simple and cheap, but the entire network fails if that one shared cable breaks.
• Tree Topology — Star networks connected together in a hierarchy, branching out from a root — combining Star's per-device reliability with the ability to scale to a much larger network.
• Mesh Topology — every device connects directly to every other device. Highly reliable (many alternate paths if one connection fails), but expensive and complex to wire as the network grows.

Explanation

Each topology trades reliability against cost and complexity differently: Bus is cheapest but has a single point of failure shared by everyone; Star isolates individual device failures but still depends entirely on its one central device; Mesh has no single point of failure at all, at the direct cost of needing far more connections to wire up. Tree is really Star repeated at a larger scale, which is exactly why it inherits Star's own trade-off, just applied hierarchically.

Note: "Single point of failure" is the concept CBSE tests most directly here — know exactly which topology fails completely from one broken connection (Bus, and Star's central device) versus which tolerates it (Mesh, and Star's individual device links).

Summary

Star connects every device to one central point; Bus shares one single cable; Tree is Star networks arranged hierarchically; Mesh connects every device directly to every other — each trades reliability against cost and wiring complexity differently.

Introduction

"The Internet" and "the Web" are often used as if they mean the same thing — this topic covers exactly what each one actually is, and how they relate.

Concept

• Internet — the vast, global network of interconnected networks (the largest WAN, from earlier in this chapter) — the physical and logical infrastructure connecting billions of devices.
• World Wide Web (WWW) — a system of interlinked documents (web pages), accessed over the Internet using web browsers — one specific application that runs on top of the Internet's infrastructure, not the infrastructure itself.
• Other applications also run over the same underlying Internet: email, instant messaging, video calling, and many more.

Explanation

The Internet is the road network; the Web is one specific kind of traffic that travels on it — email and video calls are other traffic on that exact same road, using the Internet's infrastructure just as much as web browsing does, but through entirely different applications and protocols. The Web became so dominant that its name gets used loosely for the Internet itself, but they are not, and were never, the same thing.

Note: The Web existing at all depends on the Internet already existing — but the Internet existed, and other applications like email already ran over it, before the Web itself was invented.

Summary

The Internet is the global network infrastructure itself; the World Wide Web is one application built on top of it — a system of interlinked documents accessed via browsers. Email, messaging, and video calling are other applications running over that same underlying Internet, not the Web itself.

Introduction

This closing topic of the chapter covers the software you actually use to browse the Web from the last topic, and three features every modern browser has.

Concept

A web browser is the application software that requests and displays web pages — Chrome, Firefox, and Edge are common examples.

• Settings — configurable browser preferences: default search engine, homepage, privacy controls, and more.
• Add-ons (Extensions) — small, optional programs installed into a browser to add extra features (an ad blocker, a password manager).
• Cookies — small pieces of data a website asks the browser to store on your device, so the site can recognise you on a later visit (staying logged in, remembering site preferences).

Explanation

Cookies exist to work around a genuine limitation: a website, on its own, has no memory of you between separate visits — a cookie is what lets it "remember" you were there before, by having your own browser store and hand back a small piece of identifying data on each new request. This convenience is also exactly why cookies are a recurring privacy topic — the same mechanism that keeps you logged in is what also lets a site (or a third party) track your visits over time.

Note: An Add-on genuinely changes what a browser can do; a Setting only changes how the browser's existing features already behave — installing an ad blocker is an Add-on; changing your default search engine is a Setting.

Summary

A web browser requests and displays web pages. Settings configure the browser's own existing behaviour; Add-ons install new features into it; Cookies let a website store small pieces of data on your device so it can recognise you across separate visits.