ICT IGCSE Study Notes: Chapter 4 - Networks and the Effects of Using Them

Hello future ICT expert! This chapter is all about how computers talk to each other. Networks are everywhere—they let you stream videos, play games online, and even check your social media.
Understanding networks is crucial because nearly all modern ICT relies on them. Don't worry if the devices and terms sound technical; we will break them down using simple analogies!

4.1 Networks: The Building Blocks

What is a Network?

A network is simply two or more devices (like computers, phones, or printers) connected together to share resources and exchange information.

The Traffic Controller: The Router

If a network is a system of roads, the router is the traffic police officer directing where all the data (the "traffic") needs to go.

Purpose and Operation of a Router

The router has three main jobs, according to the syllabus:

  1. Connecting networks and devices to the internet: It acts as the gateway between your local network (like your home Wi-Fi) and the massive worldwide network (the Internet).
  2. Storing computer addresses: It keeps a list of all devices connected to it (their IP addresses), so it knows exactly where to send information.
  3. Routing data packets: It examines the address on each data packet and decides the most efficient path (route) for that packet to travel to its destination.

Think of data packets as letters: the router reads the address and puts them on the quickest delivery route.

Common Network Devices

Besides the router, several other devices help a network function smoothly:

  • Network Interface Card (NIC): This is a circuit board installed in a device (like your laptop or desktop) that allows it to connect to a network. Every device needs one, whether for wired (Ethernet) or wireless (Wi-Fi) connections.
  • Hub: A very basic, older device that connects multiple computers. When a hub receives data, it sends it out to every single device connected to it. This wastes bandwidth and is slow.
  • Switch: Much smarter than a hub. A switch receives data and sends it only to the intended destination device by checking its MAC address. This improves network efficiency and security.
  • Bridge: Used to connect two separate LANs (Local Area Networks) that use the same protocol, making them look like a single network.

Quick Review: Hub vs. Switch
A Hub is like shouting information in a room (everyone hears it). A Switch is like whispering it directly to the right person.

Understanding Network Types (LAN, WAN, Environments)

Network Types: Size Matters!

Networks are categorised mostly by how geographically large they are:

  • Local Area Network (LAN): A network spread over a small geographical area, such as a school building, office, or home. They are usually fast.
  • Wireless Local Area Network (WLAN): Essentially a LAN, but using Wi-Fi radio waves instead of physical cables to connect devices.
  • Wide Area Network (WAN): A network spread over a large geographical area, connecting multiple LANs together. The best example of a WAN is the Internet itself! WANs rely heavily on routers to direct traffic over long distances.

Analogy: A LAN is your school campus. A WAN is the network that connects your school campus to the bank headquarters across the country.

Wi-Fi and Bluetooth

Both Wi-Fi and Bluetooth allow wireless connections, but they are used for very different things:

Feature Wi-Fi (Wireless Fidelity) Bluetooth
Main Use Connecting devices to the Internet and local networks. Pairing personal devices (e.g., phone to headphones, keyboard to tablet).
Range Medium to Long (Up to 100 metres). Very Short (Usually 10–30 metres).
Speed High-speed data transfer (Good for streaming). Lower speed data transfer (Good for small data/audio).

Similarities: Both use radio waves to transmit data wirelessly and are governed by international standards.

Differences: Wi-Fi is built for high bandwidth and covering larger areas, while Bluetooth is built for low power consumption and short-range device pairing.

Common Network Environments

We often talk about the 'net', but there are three distinct types of networks based on access:

  1. The Internet: This is the global network, publicly accessible, used by anyone with a connection.
  2. Intranet: A private network, accessible only by authorised staff within an organisation (e.g., your school's internal network where staff share documents). It uses Internet protocols (like HTTP) but is strictly firewalled off from the public Internet.
  3. Extranet: An extension of an Intranet, which allows selected external users (like suppliers, partners, or specific customers) controlled access to certain parts of the internal network.

Memory Trick:
Internet = International/Public.
Intranet = Intranal/Private.
Extranet = Extra Access (for specific outside partners).

Cloud Computing

Cloud computing means storing, managing, and processing data on remote servers hosted on the Internet, rather than on your local computer or server. Think of it like renting a digital storage locker far away.

Characteristics and Uses of Cloud Computing

  • How data is stored: Data is stored on massive server farms (data centres) owned by companies like Google or Microsoft. The data is duplicated across several servers for safety.
  • How data is managed: The cloud provider manages all the hardware, maintenance, security, and software updates.
  • How data is shared: Users access their data using an internet connection and a login account. This makes sharing files with collaborators very easy.

Advantages and Disadvantages of Cloud Storage

It's important to compare cloud storage against traditional local storage (like saving files on your own hard drive):

Advantages (A)
  • Accessibility: Access data anywhere, anytime, using any device with an internet connection.
  • Scalability: You can instantly increase your storage capacity without buying new hardware.
  • Backup/Disaster Recovery: Data is automatically backed up, protecting against local device failure (like your laptop crashing).
  • Cost: You only pay for the storage you use (subscription model).
Disadvantages (D)
  • Reliance on Internet: If you lose your connection, you lose access to your data.
  • Security Risks: You hand over control of your data security to a third-party provider. Although providers are usually secure, there is always a risk of hacking.
  • Control: You have less control over the physical location and management of your data.

4.2 Network Issues and Communication (Security and Safety)

Security Issues Regarding Data Transfer

When data moves across a network, we need to protect two key things:

  • Privacy: Ensuring that data containing personal information (e.g., your name, address, medical records) is protected from unauthorised access.
  • Confidentiality: Ensuring that sensitive data (e.g., company secrets or private communication) remains secret and is only viewed by the intended recipient.

We use methods like encryption (scrambling data) and strong authentication to maintain privacy and confidentiality.

Passwords: The First Line of Defence

Passwords are vital, but they must be strong to be effective.

Strong vs. Weak Passwords
  • Strong Password Characteristics:
    • Lengthy (12+ characters is ideal).
    • Mix of upper and lower case letters.
    • Includes numbers and symbols.
    • Does not contain personal information (like your name or birthday).
  • Weak Password Characteristics: Short, common words, predictable sequences (e.g., "123456" or "password").
Avoiding Password Interception

To protect your passwords:

  • Regularly change your passwords.
  • Use up-to-date anti-spyware software, which detects and removes programs designed to secretly record your keystrokes (key logging).

Other Authentication Methods

Passwords aren't the only way to prove you are who you say you are:

  • Biometric Methods: Using unique physical characteristics (fingerprints, iris scans, voice recognition).
  • Smart Cards: Cards with an embedded microchip that stores data securely (e.g., Chip and PIN bank cards).
  • Magnetic Stripes: Found on older cards, storing limited data that can be read by swiping.
  • Physical Tokens: Small devices that generate a constantly changing, one-time security code.
  • Electronic Tokens (Digital Certificates): Files used to verify the identity of a website or user during a secure transaction.
  • Zero Login: A system where authentication is handled automatically based on trusted factors (like the device you are using or your location), reducing the need for manual passwords.

Did You Know? Two-Factor Authentication (2FA) is now standard. This requires two different methods of proof (e.g., password + a code sent to your phone). This dramatically increases security!

Anti-Malware Software

Malware (Malicious Software) includes viruses, spyware, and ransomware. We use anti-malware and anti-virus software to protect our systems.

Operation of Anti-Malware Software:

The software works by:

  1. Scanning: Checking files, downloads, and storage media (like USB drives) for known malware signatures.
  2. Quarantining: Isolating suspicious or infected files in a safe place so they cannot harm the system.
  3. Removing: Deleting the malware from the system.
  4. Updating: The software must be regularly updated to recognise the latest viruses and threats.

Common Mistake to Avoid: You must ensure you scan any storage media (like flash drives) used to transfer data *before* you open files from them!

Electronic Conferencing

Electronic conferencing allows people in different locations to communicate interactively over a network.

Types of Conferencing:
  • Video-conferencing: Uses video and audio to connect two or more locations (e.g., a formal meeting over Zoom).
  • Audio-conferencing: Only uses sound/voice (like a group phone call).
  • Web-conferencing: Often involves screen sharing, presentations, and interactive chat alongside audio/video (used for webinars or online training).
Advantages:
  • Saves travel time and costs.
  • Allows for faster decision-making between geographically distant teams.
  • Easy sharing of documents/screens during the conference.
Disadvantages:
  • Requires fast, reliable broadband connection.
  • Technical issues (lag, sound problems) can disrupt the meeting.
  • Time zone differences can make scheduling difficult.
Hardware, Software, and Network Required:
  • Hardware: Microphone, speakers/headphones, camera (for video conferencing), and a monitor/screen.
  • Software: Dedicated conferencing application (e.g., Microsoft Teams, Google Meet).
  • Network Connection: A high-speed internet connection with high bandwidth (the capacity to transfer data) is essential for smooth video and audio.

Key Takeaway from Networks

Networks are complex systems that enable global communication. Remember the key components (router, NIC, switch) and understand how network scale (LAN vs WAN) and security measures (passwords, anti-malware) impact our use of ICT every day. You've got this!