Networks and Digital Communication

By Soleha Majeed

Multiple Choice

Which of the following is an example of a network?

• A single computer

• A printer that is turned off

• A smartwatch connected to a phone

• A disconnected router

Multiple Choice

Which of these is not a wireless technology?

• Bluetooth

• Cellular

• Wi-Fi

• Ethernet

Chp 3: Networks and Digital Communication - pg 231

By Soleha Majeed

Introduction to Networks and Digital Communication

• A network connects devices together, either by wires or wirelessly.

• Networks allow devices to share data and resources.

• Examples: connecting a computer to a printer or accessing the internet.

Types of Networks

• Main types: PAN, LAN, WAN

• PAN: Small personal network, few devices, close together.

• LAN: Covers a building or a few buildings, many devices.

• WAN: Covers a large geographical area, connects many LANs (e.g., the internet).

Multiple Choice

Which network connects devices within a single building?

• WAN

• LAN

• PAN

• VPN

Personal Area Network (PAN)

• Small network, usually in one room.

• Few devices, e.g., phone to smartwatch or laptop to printer.

• User owns the network hardware.

• Examples:

  • Zara’s smartwatch syncing with phone via Bluetooth.

  • Marcus’s laptop connected to a printer via cable.

Multiple Choice

Who usually owns the hardware in a PAN?

• The internet service provider

• A company

• Government

• The user

Local Area Network (LAN)

​Connects multiple devices in the same building or site.

• Devices are close together and can use wired or wireless connections.

• Hardware is owned by the user or organization.

• Example:

  • Arun’s family devices connected to a shared storage at home via Wi-Fi.

Multiple Choice

What is the typical location of devices in a LAN?

• Different countries

• Across cities

• Within a single building or site

• Between planets

Multiple Choice

Which of these is an example of a LAN?

• Devices connected between two countries

• A smartwatch connected to a phone

• A home network with several devices connected to a router

• A network on an airplane

Written task:​

Complete 3.1 questions (pg 233) in your notebooks

Wide Area Network (WAN)

• WAN connects devices across large geographical areas (towns, cities, countries).

• Devices can use wired, wireless, or both types of connections.

• Ownership: Some hardware belongs to the user, but much belongs to ISPs or companies.

• Examples:

  • Sofia and Marcus video chatting across a city using the internet.

  • Video streaming services delivering content nationwide.

  • The internet is the largest WAN.

How internet access is provided

Step 1:
Connection to the ISP: At home or in a business, your router or modem connects to the ISP’s network using a wired line (like fiber or copper cable) or wireless link (like 4G/5G towers).

How internet access is provided

Step 2:
Data transmission: When you visit a website or stream a video, your request goes through the ISP’s network to the servers where the data is stored, and the ISP delivers the data back to your device.

How internet access is provided

Step 3:
Infrastructure sharing: In WANs, ISPs connect many smaller networks (like home LANs) together, forming part of the global internet.

WAN

• WANs often connect smaller networks (LANs) together.

• Uses routers, WAPs, underground cables, and ISP infrastructure.

• Connections involve multiple owners: families, businesses, ISPs, service providers.

Multiple Choice

Why is the internet considered a WAN?

• a) It only connects devices in one location.

• b) It uses one type of cable to connect devices.

• c) It connects billions of devices worldwide using varied infrastructure

• d) It is owned by one organization.

Written task:​

Questions 3.3: pg 236 TO BE DONE IN NOTEBOOKS

Comparison of PAN, LAN, and WAN

​PAN:
Few devices, close range, owned by user.

​LAN:
Many devices, same building/site, owned by user or organization.

​WAN:
Many devices, spread across cities or countries, multiple owners including ISPs.

Multiple Choice

Which scenario best describes WAN?

• A family sharing photos on home Wi-Fi.

• A smartwatch syncing with a phone.

• A streaming company providing content nationwide.

• A laptop printing via cable.

Wired Connections Overview

• Networks can use wired or wireless connections.

• Wired connections use physical cables like copper or fibre optic.

• Copper cables transmit data using electrical signals; fibre optic uses light.

Copper Cables

• Made of thin copper strips.

• Speed: Up to ~300 Mbps.

• Advantages: Cheap, easy to install.

• Disadvantages: Thicker, prone to electromagnetic interference.

• Examples: Ethernet cables, HDMI, phone chargers.

Multiple Choice

What is a major limitation of copper cables compared to fibre optic?

• Cannot transmit audio

• Limited by electromagnetic interference

• Cannot connect to routers

• Not compatible with phones

Fibre Optic Cables

• Made of thin glass strands.

• Speed: Can reach 10 Gbps or more.

• Advantages: Faster, immune to interference, thinner.

• Disadvantages: Expensive, harder to install.

Read page 239

Multiple Choice

Why might fibre optic cables be preferred over copper for long distances?

• They are cheaper and easier to install

• They are unaffected by electromagnetic interference and offer higher speeds

• They transmit electrical signals more efficiently

• They are thicker and more durable

Wired vs Wireless Connections pg 31

• Wired: Reliable, secure, faster, more expensive, harder to add devices.

• Wireless: Easier to add devices, cheaper, less secure, slower, can be affected by interference.

Open Ended

Students research examples of where copper and fibre optic are commonly used (home, city, undersea).

Network Devices

Router, Switch, Hub, Modem, Access Point, NIC, Cables

Introduction to Network Devices

• Networks use special devices to connect and share data.

• Common devices: Router, Switch, Hub, Modem, Access Point, NIC, and Cables.

• Each has a different role in making communication possible.

Without these devices, the internet wouldn’t work.
Think of a transport system. Different vehicles/roads control how traffic moves just like these devices manage data traffic.

Multiple Choice

Which of the following is NOT a network device?

• Router

• Hub

• Modem

• Keyboard

Router

• Connects different networks (e.g., home network → Internet).

• Routes data packets to the correct destination.

• Example: Your Wi-Fi router at home connects your devices to the internet.

Multiple Choice

The main role of a router is to:

• Connect devices inside the same network

• Route data between different networks

• Store data permanently

• Provide backup power

Switch

• Connects multiple devices in the same network.

• Sends data directly to the device that needs it (efficient).

• Example: Office switch connecting computers & printers.

Hub

• Old device, similar to a switch.

• Sends data to all devices in the network (less secure, slower).

• Example: Early computer labs often used hubs.

Hub VS Switch (Analogy)

• Hub = announcing to the whole class

• Switch = whispering to the right student.

Multiple Choice

A switch is more efficient than a hub because it:

• Sends data to all devices

• Stores data like a hard drive

• Connects networks to the internet

• Sends data only to the intended device

Multiple Choice

Why are hubs less secure than switches?

• They store all files

• They send data to all devices, not just the target one

• They connect to the internet directly

• They require more cables

Modem

• Converts signals from your Internet Service Provider (ISP) into usable internet data.

• Connects your home to the internet line (telephone/fiber/cable).

• Example: DSL modem for home internet.

Without a modem, a router cannot access the internet.

Analogy: Modem = translator between your house and ISP.

Multiple Choice

What is the main job of a modem?

• Store emails

• Encrypt data packets

• Connect multiple computers inside a network

• Translate signals from ISP into internet connection

Access Point (AP)

• Extends wireless connectivity (Wi-Fi) in a network.

• Allows devices to connect without cables.

• Example: Wi-Fi hotspot in a library.

Router provides internet, AP extends Wi-Fi coverage.

Example: Wi-Fi in school hall connected via AP.

Multiple Choice

What is the main use of an Access Point?

• Extend Wi-Fi coverage

• Store files

• Route emails

Physical medium for wired communication.
Common types: Ethernet cables (LAN), Fiber optic cables.

Cables

A hardware component inside a computer/device.

Eg: Every laptop/desktop has a NIC (Ethernet port or Wi-Fi card).

NIC

Multiple Choice

Why might schools prefer Ethernet cables for desktops?

• They are slower but cheaper

• They require no router

• They are wireless

• They are more stable and secure

Data Transmission and Security

Errors in Data Transmission

• Data can get corrupted when moving between devices.

• Causes of errors:

  • Interference (radio signals, other devices).

  • Crosstalk (overlapping signals in cables).

  • Weak signals (distance, poor quality cables).

• Errors may change bits of data (0 ↔ 1), making information inaccurate.

​A real example: A student sends homework by email, but due to errors, the file gets corrupted and won’t open.

Multiple Choice

Which of the following is NOT a cause of data transmission errors?

• Interference

• Crosstalk

• Weak signals

• Strong encryption

Echo Check (Error Detection)

• Method to detect data transmission errors.

• Steps:

  1. Sender sends data to receiver.

  2. Receiver sends back a copy of the received data.

  3. Sender compares original with copy.

  4. If data matches → no error.

  5. If data doesn’t match → error detected → resend.

Example:

Original: 110111
Copy received: 110011

Mismatch → Error → Resend.

​Send → Copy received → Compare → If same (OK), If different (Resend).

Multiple Choice

In echo checking, who compares the original data with the returned copy?

• The sender

• The receiver

Antivirus and Antispyware (Security Method 2)

• Antivirus → Detects and removes viruses (harmful software).

• Antispyware → Detects and removes spyware (steals information like passwords).

• How they work:

  1. Scan files and downloads.

  2. If virus/spyware found → alert user.

  3. File quarantined (isolated).

  4. User can delete or keep file.

Example:
Downloading a free game → Antivirus detects a Trojan virus → moves it to quarantine → Safe.

Multiple Choice

Which of the following is the BEST description of a firewall?

• A device that fixes corrupted data

• A program that scans for viruses

• A barrier that checks incoming and outgoing data

Firewalls (Security Method 1)

• Definition: A barrier (hardware or software) that protects data.

• How it works:

  • All data entering computer is checked.

  • If safe → allowed.

  • If unsafe → blocked.

• Acts like a bodyguard for your computer.

• Prevents hackers and harmful data from entering.

Example:
Firewall blocks unknown website from sending harmful data.

Multiple Choice

Why is quarantine used in antivirus software?

• To delete safe files automatically

• To hide files from hackers

• To compress data for faster transfer

• To isolate infected files so they cannot harm the system