OCR J277 · Component 1 · Topic 1.3.1a

LAN, WAN & Network Performance

What Is a Network? · LANs & WANs · Examples · Factors Affecting Performance · Exam Practice

CSZone OCR GCSE Computer Science J277

Learning Objectives

By the end of this video you will be able to...

Explain what a network is, and describe the difference between a LAN and a WAN

Describe the characteristics of LANs and WANs, including common examples of each

Compare a LAN and a WAN in terms of size, ownership and use

Explain how the number of devices connected to a network affects its performance

Explain how bandwidth affects network performance, and apply this to a given scenario

⚡ This is part 1 of 4 covering 1.3.1 — Networks and topologies.

What Is a Network?

Two or more devices, connected together

DEFINITION

A network is two or more computers or devices connected together so they can communicate and share resources, such as files, printers, or an internet connection.

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Networks come in different sizes. OCR J277 focuses on two key types: LAN — Local Area Network — and WAN — Wide Area Network.

⚡ The key difference between a LAN and a WAN is the geographical area the network covers.

Local Area Network

LAN — a network in one place

DEFINITION

A LAN (Local Area Network) covers a small geographical area, such as a single building or site.

A LAN is usually owned, set up and maintained by the organisation or person that uses it — for example, a school's IT department manages its own LAN.

Common examples: a school network connecting classroom computers, a home network connecting a laptop, phone and smart TV, or an office network within a single building.

⚡ If you can imagine all the devices being in (or very near) the same building, it's almost certainly a LAN.

Wide Area Network

WAN — networks connected over distance

DEFINITION

A WAN (Wide Area Network) covers a large geographical area, often connecting multiple LANs together over long distances — for example, between cities or countries.

Because the distances involved are so large, a WAN typically relies on infrastructure provided by third parties, such as telecommunications companies, rather than being owned entirely by one organisation.

Common examples: a company with offices in different cities connected together, a bank linking its branches nationwide, and — the largest WAN of all — the Internet itself.

⚡ The Internet is a WAN made up of countless smaller networks (including many LANs and WANs) connected together.

LAN vs WAN

Comparing LANs and WANs

	LAN	WAN
Geographical area	Small — one site or building	Large — cities, countries

Ownership

Usually one organisation

Often shared / third-party infrastructure

Typical example

A school's network

The Internet

⚡ Exam tip: if asked to compare, give a clear point of difference for each row — size, ownership and example — rather than just restating the definitions.

Examples in Context

Spotting LANs and WANs in a scenario

SCENARIO A

"A college has computers in its library, classrooms and offices, all connected together so staff and students can access shared files and printers."

This is a LAN — all the devices are within one site, and the college's own IT staff set up and maintain it.

SCENARIO B

"The same college also has a second campus 50 miles away, and the two sites are linked so staff can access the same shared systems from either location."

⚡ The link between the two campuses is a WAN — it connects two LANs together over a large distance, most likely using a third-party provider's infrastructure.

Performance Factor 1

Number of devices connected

KEY IDEA

A network has a limited amount of capacity to share. The more devices connected, the more devices there are competing for that same capacity.

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If a network has a fixed amount of capacity, and more devices are sending and receiving data at the same time, each device effectively gets a smaller share of that capacity.

⚡ This is why a home Wi-Fi network can feel slower in the evening, when more devices in the house are streaming, gaming or browsing at once.

Performance Factor 2

Bandwidth

DEFINITION

Bandwidth is the amount of data that can be transferred over a network connection in a given amount of time.

Low bandwidth

slow

High bandwidth

fast

A higher bandwidth means more data can be transferred at once, so the network can support more traffic without slowing down.

⚡ Bandwidth and number of devices are linked: if bandwidth stays the same but more devices join the network, each device gets a smaller share — so performance can drop.

Exam Practice

Exam-Style Questions — LAN, WAN & Performance

Question 1 · 1 mark

State what the abbreviation "LAN" stands for.

1 mark

ANS

Local Area Network.

Question 2 · 2 marks

Describe one difference between a LAN and a WAN.

2 marks

ANS

A LAN covers a small geographical area, such as a single site or building, whereas a WAN covers a large geographical area, such as multiple cities or countries.

Question 3 · 3 marks

An office network has become slower since ten new laptops were connected to it. Explain why this might happen, and suggest how the issue could be reduced.

3 marks

ANS

More devices are competing for the same bandwidth, so each device gets a smaller share and performance drops. Increasing the bandwidth available to the network would give each device a larger share, reducing the slowdown.

Common Mistakes

Four mistakes that cost marks

Defining a LAN or WAN only by "size" without explaining what that means. Be specific: a LAN covers a single site or building; a WAN covers a large geographical area such as multiple cities or countries.

Saying the Internet is "a website" or "a single network." The Internet is the largest WAN — a worldwide collection of interconnected computer networks, not one network or one website.

Confusing bandwidth with the number of devices. Bandwidth is the amount of data that can be transferred in a given time; the number of devices is how many things are competing to use that bandwidth. They're related, but not the same thing.

Only naming a performance factor without explaining its effect. "Bandwidth" alone isn't enough — explain that higher bandwidth allows more data to be transferred, improving performance, and vice versa.

Summary

1.3.1a — LAN, WAN & Network Performance

NETWORK

Two or more devices connected to share data and resources.

LAN

Small area, e.g. a school or office. Usually owned by one organisation.

WAN

Large area, e.g. the Internet. Often uses third-party infrastructure.

PERFORMANCE

Affected by number of devices connected and bandwidth available.

⚡ Exam tip: be ready to apply LAN/WAN and performance factors to scenarios, not just define them.

CSZone.co.uk

That's 1.3.1a done.

Next up: 1.3.1b — Network Types & LAN Hardware

Full quiz, marked worksheet and slides at CSZone.co.uk