IGCSE ICT: Networks and the Effects of Using Them — Revision Notes

Condensed for the final weeks, spanning both halves of Topic 4. For the full explanation, use the Networks study guide (4.1) and the Network Issues and Communication study guide (4.2).

4.1 The router — three named functions

Connects networks/devices to the internet; stores computer addresses; routes data packets toward their destination. Learn all three separately — mark schemes credit each one.

4.1 Other network devices

NIC — lets a device connect to a network at all. Hub — broadcasts to every connected device regardless of intended recipient (simple, inefficient). Switch — learns which device is on which port, sends data only to the intended recipient (efficient). Bridge — joins two network segments into one.

4.1 Wi-fi vs Bluetooth

Wi-fi: connects a device to a wider network/internet, larger range. Bluetooth: connects two devices directly to each other, short range, no network infrastructure needed (headphones, wireless keyboard).

4.1 Cloud computing

Advantages: accessible from any internet-connected device; reduced reliance on local storage hardware. Disadvantages: depends on a working internet connection; relies on a third-party provider for security and availability.

4.1 Extranet, intranet, internet

Intranet — private, internal to one organisation only. Extranet — private network extended for controlled external access (suppliers, customers). Internet — global, publicly accessible. Same underlying technology throughout; what differs is who is permitted to access it.

4.1 LAN, WLAN, WAN

LAN — small area (one building/site), cabled. WLAN — wireless equivalent of a LAN, same small area. WAN — much larger area, connects multiple LANs across sites/cities/countries (the internet is the largest WAN).

4.2 Passwords

Strong = long + mixed character types (upper/lower/number/symbol) + avoids personal info. Weak = short, one character type, or guessable (name/birthdate). Regular changes limit how long a compromised password stays useful. Avoid interception with up-to-date anti-spyware.

4.2 Authentication beyond passwords

Zero login — passive signals (typing pattern, location, device recognition), no active entry. Biometric — fingerprint, iris, facial recognition. Magnetic stripe / smart card — data on a physical card, read by a reader. Physical token — separate hardware (keyfob generating a one-time code). Electronic token — equivalent code via an app.

Framework: “something you know” (password) + “something you have” (token/card) + “something you are” (biometric) = stronger multi-factor authentication.

4.2 Anti-malware

Removes/quarantines viruses; scans storage media used to transfer data; scans downloads. Must be kept up to date — it relies on a database of known malware signatures, so it cannot recognise malware discovered after its last update.

4.2 Electronic conferencing

Video-conferencing — camera, microphone, speaker, software, fast connection; suits seeing participants adding value (interview, negotiation). Audio-conferencing — microphone + speaker only, lower bandwidth; suits no visual need, cost/reliability matters more. Web-conferencing — adds document/screen sharing to audio/video; suits collaborative sessions needing shared live material.

Worked example: matching the tool to the need

A company holds a weekly meeting reviewing a shared spreadsheet with staff across three countries, and a daily supplier catch-up needing only a spoken update. Weekly meeting → web-conferencing (needs to see/discuss the same live document — audio/video alone can’t provide this). Daily catch-up → audio-conferencing (only a spoken update needed; video/web-conferencing would be unnecessary cost and complexity).

Worked example: classifying a described network

A school connects its three campuses across a city, lets students access shared coursework wirelessly within each campus building, and allows a small number of approved textbook suppliers to upload new resources. Within one campus building, wireless student access is a WLAN. Connecting the three campuses across the city is a WAN (multiple sites, larger geographic area). The supplier upload system is the clearest case for an extranet — controlled, limited external access to specific resources, not a fully public internet system or a fully closed internal-only intranet. Practising this kind of combined classification, rather than revising each term in isolation, is the best check that the distinctions are genuinely understood.

Why 4.2 depends on 4.1

The security and communication content in 4.2 exists specifically because data travels across the shared network paths described in 4.1 — LANs, WLANs, WANs, and the internet — where interception is possible. Electronic conferencing likewise depends on having a network connection (and, for video specifically, a sufficiently fast one) already in place. Treat 4.1 and 4.2 as one connected picture — “what can go wrong on the network, and how communication tools use that same network” — rather than two disconnected topic lists.

Exam traps

• Vague “connects to the internet” for a router instead of naming all three functions.
• Confusing hub/switch/bridge — broadcast-to-all vs directed-to-recipient vs joining-two-segments.
• Extranet vs intranet — extranet allows controlled external access; intranet is internal-only.
• Naming an authentication method without placing it in the know/have/are framework.
• Forgetting anti-malware’s update-dependency as a specific, statable fact.
• Choosing video/web-conferencing by default when a scenario only needs audio — match hardware to actual need.

Self-test

1. Name the router’s three functions.
2. Distinguish a hub from a switch.
3. What is the key difference between an intranet and an extranet?
4. Give the “three somethings” framework for authentication.
5. Why must anti-malware software be kept up to date?
6. A company needs staff in five offices to jointly edit a shared document while talking. Which conferencing type, and why?

Answers: 1. Connecting networks/devices to the internet; storing computer addresses; routing data packets. 2. A hub broadcasts to every connected device; a switch learns which device is on which port and sends data only to the intended recipient. 3. An intranet is accessible only within one organisation; an extranet extends controlled access to specific external parties while still restricting general public access. 4. Something you know (password), something you have (token/card), something you are (biometric). 5. It relies on a database of known malware signatures, so it cannot recognise malware discovered after its last update. 6. Web-conferencing — staff need to view and edit the same live document together, which audio- or video-conferencing alone cannot provide.