g6:Networks and digital communication

​Chp 3: Networks and digital communication

By Soleha Majeed

What is a Network?

A network is a group of two or more devices (computers, phones, tablets, printers, etc.) that are connected together so they can share data, resources, and services.

Examples:

• School computers connected to a printer

• Internet (the largest network in the world)

• Wi-Fi at home connecting phones and laptops

Multiple Choice

Which of the following best defines a computer network?

• A single computer used for personal work

• A system where devices are connected to share data and resources

​Imagine you're at a restaurant. You, the customer, ask the waiter (the server) to bring you food. The waiter then goes to the kitchen, gets the food, and serves it to you.

​Imagine

Question: Who is the server in this case? and What is the service?
Who is the client?

What is a server?

A server is a computer program or device that provides a service to another computer program and its user, also known as the client.

Each server has one delegated task

What is a Server?

• A server is a networked device that "serves" data to other devices.

• Other devices (computers, tablets, phones) can request data from the server.

• Servers reduce the need to store everything on personal devices.

Examples:

• Email server: Stores your emails.

• Web server: Hosts websites you visit.

Multiple Choice

A server is mainly used to:

• Store only videos

• Work as a single personal computer

• Serve data to other devices on a network

• Replace the internet

Types of Data Stored on Servers

Servers can store many types of data:

• Web pages (for websites)

• Emails (school or personal accounts)

• Documents (assignments, reports)

• Video & audio (streaming services)

• Messaging services (chat systems like WhatsApp or school intranet)

Open Ended

“If our school server was switched off for a day, what services would we lose?”

Multiple Choice

Which of these cannot be stored on a server?

• A physical object (e.g., furniture)
• Emails

• A database file
• Streaming files

Streaming Services

• Streaming = watching or listening to media online without storing it on your device.

• Files (movies/music) play directly from a server over the internet.

• Needs large storage capacity because high-quality media takes lots of space.

Example:

• Netflix users spend 164 million hours per day streaming videos worldwide!

Multiple Choice

Why do streaming servers need large storage capacity?

• Because media files are small

• Because high-quality videos take up a lot of space

• To back up games only

• To store apps

Messaging Services

• Direct messaging = quick communication between users.

• Used in companies, schools, or apps (e.g., WhatsApp, MS Teams).

What's an Intranet?

• An intranet is a private network just for a specific group, like your school's network.

• It's like having a VIP club online where only members can enter and share things.

  
  https://www.youtube.com/watch?v=dIA1KweJoRY

Multiple Choice

Is the intranet and internet same?

• No, the intranet and internet are not the same.
• Yes, they are the same.

Private access for organization members only.


Think of this as a Club. Only people with membership can access

Intranet:

• Public access for everyone.
  
  Think of this as a public park. Anyone can access the park

Internet:

Summary

Multiple Choice

What is the main difference between an intranet and the internet?

• The internet is global, intranet is private to an organization

• Both are the same

• Intranet requires no devices

• Internet has no servers

Notebook work:

Multiple Choice

Which server stores learners’ assignments and homework?

• Email server

• Web server

• Document server

• Streaming server

Why Do Schools Need Different Servers?

• Web server → hosts the school website.

• Email server → school emails for staff & students.

• Document server → stores learners’ work.

• Devices must be connected to the right server for proper services.

Example: If the email server is down → no emails.

“Why is it better to have shared servers instead of saving everything on one computer?”

Multiple Choice

Which server is most important for a school to communicate with parents?

• Web server

• Document server

• Email server

• Wi-Fi route

Transferring Data Between Devices

• Data can be transferred in two ways:

  1. Wired (Ethernet cable)

  2. Wireless (radio waves)

• Example: A computer at home can connect to the router with an Ethernet cable OR Wi-Fi.

​Ethernet cable

Radio waves

Multiple Choice

Which connection uses radio waves to transfer data?

• USB cable

• Wi-Fi

• HDMI cable

• Ethernet

Cellular Networks

• Cellular network = worldwide network of communication towers.

• Phones connect to the nearest cell tower using radio waves.

• Services: calls, SMS, internet browsing, streaming, GPS navigation.

What happens when you have no Wi-Fi? How does your phone still work?

Multiple Choice

What do mobile phones connect to when Wi-Fi is not available?

• Ethernet

• GPS satellite

• Cell tower

• Web server

Multiple Choice

Which device can use both Wi-Fi and cellular network?

• Smart phones

• Desktop computer

• Smart TV

• Printer

GPS & Satnav

• GPS (Global Positioning System) = network of satellites.

• Phones + cellular network + GPS = satellite navigation (satnav).

• Used for maps, directions, finding lost devices.

https://www.youtube.com/watch?v=RSA3feQ9gKk

Multiple Choice

Which technology is used for satellite navigation on phones?

• GPS

• Wi-Fi

• Bluetooth

• Ethernet

Wi-Fi at Home

• Most homes use Wi-Fi for internet.

• Router = device that connects home network to the internet provider.

• Devices connect by:

  • Ethernet cable

  • Wireless radio waves

Multiple Choice

What device connects your home Wi-Fi network to the internet provider?

• Router

• Printer

• Switch

• Cell tower

Data Packets & Encryption

• Data is split into small pieces called packets before being sent.

• Packets travel across the network to reach destination.

• Encryption: locks the data packets so others can’t read them.

Video

Lets watch a video

Data Packets & Encryption (Analogy)

• A long letter cut into pieces, sent in different envelopes. Encryption = special lock on envelopes.

Multiple Choice

Why is encryption important when sending data?

• It makes files smaller

• It makes data easy to read

• It prevents unauthorized access to data packets

• It increases network speed

Introduction to Bandwidth

• Bandwidth is the maximum amount of data that can be transmitted between two points in a network in a specific amount of time.

• More bandwidth = faster downloads & streaming.

• Less bandwidth = slower performance

Bandwidth Analogy

Bandwidth = "network capacity."


straw example: wide straw = faster drinking, narrow straw = slower.

Multiple Choice

Bandwidth in a network refers to:

• The physical distance between devices

• The speed of the internet provider

• The maximum amount of data transmitted in a given time

• The number of devices connected

Everyday Examples of Bandwidth

• Downloading a movie:

  • Small bandwidth → takes longer.

  • Large bandwidth → quick download.

• Streaming video: higher bandwidth helps prevent buffering.

Open a video with slow buffering

What happens when many people watch Netflix at the same time at home?

Multiple Choice

Which activity requires more bandwidth?

• Browsing a webpage

• Reading an email

• Streaming a 4K movie

• Typing a document

Activity – Speed Test

• Open a speed test website (teacher shows the link).

• Record your download & upload speeds.

• Compare with classmates.

🌐 Does speed vary at different times of day?

🌐 Does speed vary at different times of day?

​✅ Yes.
Internet speed can change depending on network traffic.

Example: In the evening, many people stream videos or play online games → more demand on the internet provider’s network → slower speeds.


This is called “peak hours” (like traffic jams on the road).

Sharing Bandwidth

• Bandwidth is shared among all connected devices.

• More devices = slower performance for each.

• Example: If 4 people stream movies, internet slows down for everyone.
  smart devices (TVs, lights, plugs) also consume bandwidth.

It's like "sharing a pizza" – more people = smaller slices. 🍕

Multiple Choice

Why does your internet slow down when many devices are streaming?

• The router gets tired

• Bandwidth is shared among all devices

• The modem is overheating

• Devices need charging

Network Overload

• Too many devices demanding bandwidth → Network overload.

• Symptoms:

  • Slow data transfer

  • Pictures not loading

  • Error messages

• Even browsing can slow down if too many devices are connected.

Multiple Choice

What happens during network overload?

• Devices disconnect immediately

• Data moves slowly, pictures get stuck, errors appear

• Bandwidth increases automatically

• Internet becomes faster

Solutions to Bandwidth Issues

• Pay for more bandwidth from ISP.

• Limit high-bandwidth activities (e.g., streaming) during heavy use.

• Disconnect unused devices.

Example: Parents asking kids to stop streaming while working on video calls.

Multiple Choice

Which of these reduces bandwidth usage?

• Adding more smart devices

• Streaming in HD instead of SD

• Disconnecting unused devices

• Downloading movies during peak hours

Summary & Reflection

• Bandwidth = maximum data transfer capacity.

• More devices → shared bandwidth → slower performance.

• Network overload = when too many devices demand bandwidth.

• Solutions: increase bandwidth or manage device usage.

Multiple Choice

Which of the following best describes bandwidth?

• The size of storage on a computer

• The maximum data transfer rate of a network

Securing Data

Introduction to Securing Data

• Every day, trillions of data packets are sent online.

• Data must be kept secure so only people with permission can access it.

• Examples of data that must be secure:

  • Personal info (address, date of birth)

  • Financial info (bank details)

Multiple Choice

Which of the following needs to be kept secure online?

• Personal information, financial data, passwords, and sensitive documents
• Public social media posts
• Random website cookies
• Unencrypted emails

Caesar Cipher Activity

• Julius Caesar used a Caesar Cipher to hide military messages.

• To decode: shift letters right by 10.

• Example message: Mywzedsxq sc wi pkfyebsdo celtomd.

Decode this message with a partner. pg 175

Multiple Choice

What does encryption do?

• Speeds up internet

• Deletes unwanted data

• Hides information so only authorized people can read it

Dangers of Stolen Data

Stolen data can be misused for:

• Fraud → stealing money

• Identity theft → pretending to be you

• Phishing → tricking you to give details

• Account takeover → locking you out of your account

“Have you seen spam or fake messages?”

Multiple Choice

If someone pretends to be you using your personal information, this is called:

• Phishing

• Fraud

• Identity theft

User Authentication – Passwords

• Username + Password → basic protection.

• Strong password:

  • 3 random words

  • Mix of letters, numbers, symbols

  • Avoid personal info (name, pet, birthday)

weak password examples ("Arun123").

strong password example (“BlueTiger$Moon19”).

Multiple Choice

Which password is strongest?

• Pancake1

• Jewelpowdergenerous1234@

Fingerprint Authentication

• Every person has unique fingerprints.

• Used to unlock phones/devices.

• Hard to copy or hack.

Loops, whirls, arches are different of type patterns of fingerprints

Multiple Choice

Why are fingerprints good for authentication?

• They change every year

• Everyone’s fingerprint is unique

• They are easy to guess

Facial Recognition

• Camera scans your face shape.

• Used in smartphones and security systems.

• Works like fingerprints: compares with stored image.

Real-life: unlocking iPhones or Android phones.

"Who uses Face ID at home?”

Multiple Choice

Facial recognition works by:

• Comparing stored face image with live scan

• Reading eye color only

• Using fingerprints

Staying Safe Online

• Never share your password with anyone.

• Use strong authentication.

• Report phishing or suspicious emails.

“Did you know?”: 85% of all emails are spam/phishing.

Multiple Choice

Why should you NOT share your password with a frien

• They may forget it

• They might access your accounts