What you'll learn
This topic examines how computers connect and communicate, from small local networks to the global internet. You must understand network hardware, different topologies, security threats, and internet technologies including cloud computing and web development. CIE IGCSE Information and Communication Technology papers frequently test your ability to compare network types, identify appropriate security measures, and explain how data travels across networks.
Key terms and definitions
LAN (Local Area Network) — a network confined to a single site or building, where the organisation owns all the hardware and cabling.
WAN (Wide Area Network) — a network that covers a large geographical area, connecting multiple sites using third-party telecommunications infrastructure.
Network topology — the physical or logical arrangement of devices and connections in a network (star, bus, ring).
Router — a device that forwards data packets between different networks and connects a LAN to the internet.
Switch — a device that connects multiple devices on a LAN and uses MAC addresses to forward data only to the intended recipient.
Firewall — hardware or software that monitors and filters incoming and outgoing network traffic based on predetermined security rules.
IP address — a unique numerical identifier assigned to each device on a network (e.g., 192.168.1.1).
Protocol — an agreed set of rules that govern how data is transmitted across a network (e.g., TCP/IP, HTTP, FTP).
Core concepts
Network types: LAN vs WAN
Local Area Networks (LANs) operate within a single geographical location. A school network connecting all computers across classrooms and offices is a typical LAN. Key characteristics include:
- Organisation owns and maintains all infrastructure
- Uses cables (Ethernet) or wireless (Wi-Fi) technology
- High data transfer speeds (typically 100 Mbps to 10 Gbps)
- Low running costs after initial setup
- Limited geographical coverage
Wide Area Networks (WANs) connect geographically separated sites. A company with offices in London, Manchester and Edinburgh would use a WAN to connect these locations. Key characteristics include:
- Uses third-party telecommunications infrastructure (leased lines, satellite, cellular)
- Organisation pays ongoing rental/usage charges
- Lower data transfer speeds than LANs
- Can span countries or continents
- The internet itself is the world's largest WAN
Exam questions commonly ask you to identify which network type suits a scenario, so remember: single site = LAN, multiple sites = WAN.
Network topologies
Star topology is the most common arrangement in modern networks. Every device connects to a central switch or hub.
Advantages:
- If one cable fails, only that device is affected
- Easy to add new devices without disrupting the network
- Easy to identify faults
- Better performance as data goes directly through the switch
Disadvantages:
- If the central switch fails, the entire network stops functioning
- Requires more cabling than bus topology
- Cost of the switch adds to setup expenses
Bus topology uses a single central cable (the backbone) with all devices connected via taps or T-connectors.
Advantages:
- Requires less cabling than star
- Easy and inexpensive to set up for small networks
Disadvantages:
- If the main cable fails, the entire network fails
- Performance degrades as more devices are added
- Difficult to isolate faults
- Data collisions more likely
Ring topology connects devices in a circular chain, with data travelling in one direction.
Advantages:
- Data packets include destination address and pass through each device
- No central dependency
Disadvantages:
- If any device or cable fails, the entire network may fail
- Difficult to add devices without disrupting service
- Rarely used in modern networks
CIE examiners expect you to draw these topologies accurately and match advantages/disadvantages to specific scenarios.
Network hardware
Network Interface Card (NIC) — installed in each computer to enable network connection, either wired (Ethernet port) or wireless (Wi-Fi adapter). Each NIC has a unique MAC address (Media Access Control address) permanently assigned by the manufacturer.
Switch — operates at the data link layer, maintaining a table of MAC addresses. When data arrives, the switch forwards it only to the port where the destination device is connected. This is more efficient than a hub, which broadcasts data to all ports.
Router — connects different networks together. Your home router connects your LAN to your Internet Service Provider's WAN. Routers use IP addresses to determine the best path for data packets. They also perform Network Address Translation (NAT), allowing multiple devices on a private network to share a single public IP address.
Wireless Access Point (WAP) — allows Wi-Fi enabled devices to connect to a wired network. Often combined with routers in home networks but separate devices in large installations.
Modem — converts digital signals from computers into analogue signals for transmission over telephone lines (modulation) and converts incoming analogue signals back to digital (demodulation). ADSL and cable broadband use modems.
Server — a powerful computer that provides services to other computers (clients) on the network. Types include:
- File server: centralized file storage
- Web server: hosts websites
- Email server: manages email services
- Application server: runs software applications
Internet technologies and protocols
TCP/IP (Transmission Control Protocol/Internet Protocol) is the fundamental protocol suite for internet communication.
- IP handles addressing and routing data packets to their destination
- TCP ensures reliable delivery by checking packets arrive correctly and requesting retransmission if needed
HTTP (HyperText Transfer Protocol) — used by web browsers to request and receive web pages from servers. The address bar shows http:// before websites addresses.
HTTPS (HTTP Secure) — encrypted version using SSL/TLS certificates. Essential for secure transactions like online banking. The padlock icon in browsers indicates HTTPS.
FTP (File Transfer Protocol) — specifically designed for uploading and downloading files between computers. Web developers use FTP to upload website files to web servers.
SMTP (Simple Mail Transfer Protocol) — used for sending emails from a client to a server or between mail servers.
IMAP/POP3 — protocols for receiving emails. IMAP keeps emails on the server; POP3 typically downloads them to your device.
URL (Uniform Resource Locator) structure:
https://www.example.com:443/path/page.html
- Protocol: https
- Domain name: www.example.com
- Port: 443 (optional, default for HTTPS)
- Path: /path/page.html
DNS (Domain Name System) translates human-readable domain names (www.google.com) into IP addresses (172.217.169.36) that computers use. Your device queries a DNS server whenever you enter a web address.
Cloud computing
Cloud computing delivers computing services (storage, processing, software) over the internet rather than using local devices. The term "cloud" represents the internet.
Types of cloud services:
Software as a Service (SaaS) — applications run in the cloud, accessed through a web browser. Examples: Google Workspace, Microsoft 365, Salesforce. Users don't install software locally.
Platform as a Service (PaaS) — provides infrastructure for developers to build applications without managing underlying hardware. Examples: Google App Engine, Microsoft Azure.
Infrastructure as a Service (IaaS) — provides virtualized computing resources over the internet. Organizations rent servers, storage and networking. Examples: Amazon Web Services (AWS), Microsoft Azure.
Advantages of cloud computing:
- Access files and applications from any device with internet connection
- Automatic backups and updates managed by provider
- Pay-as-you-go pricing reduces upfront hardware costs
- Scalable storage — increase capacity without buying new hardware
- Collaboration features allow multiple users to work on same documents simultaneously
Disadvantages of cloud computing:
- Requires reliable internet connection — no access if offline
- Ongoing subscription costs may exceed one-time software purchase
- Security concerns about data stored on external servers
- Dependence on provider — if company fails, data access at risk
- Data transfer speeds limited by internet bandwidth
Network security threats and protection
Malware (malicious software) includes several threat types:
Virus — attaches to files and spreads when files are shared. Can delete files, corrupt data or make systems unstable. Requires user action (opening infected file) to activate.
Worm — self-replicating malware that spreads automatically across networks without user action. Consumes bandwidth and system resources.
Trojan horse — appears legitimate but contains hidden malicious code. Often disguised as useful software or game downloads.
Spyware — secretly monitors user activity, capturing keystrokes (keylogger), passwords, browsing habits and personal information.
Phishing — fraudulent emails or websites impersonating legitimate organizations to trick users into revealing passwords, credit card numbers or personal data. Often creates urgency ("Your account will be suspended unless...").
Pharming — redirects users from legitimate websites to fake copies, even when correct URL is entered, by corrupting DNS settings.
DDoS (Distributed Denial of Service) attack — overwhelms a server with traffic from multiple compromised computers, making websites unavailable to legitimate users.
Protection methods:
Firewall — examines data packets and blocks unauthorized access based on rules. Can be hardware (network-level) or software (individual computer).
Antivirus software — scans files and programs for known malware signatures, quarantines threats, and removes infections. Requires regular updates to recognize new threats.
Encryption — converts data into unreadable code during transmission or storage. Only authorized recipients with the decryption key can access original data. Essential for sensitive data like financial transactions.
Authentication — verifies user identity before granting access:
- Passwords (something you know)
- Biometrics: fingerprints, facial recognition (something you are)
- Security tokens, smart cards (something you have)
- Two-factor authentication (2FA) combines two methods for stronger security
Access levels — assign different permissions to users. Administrators have full control; standard users have restricted access. Prevents accidental or deliberate damage to critical files.
SSL certificates — enable HTTPS, encrypting data between browser and web server. Users should verify the padlock icon before entering sensitive information.
Regular updates and patches — software companies release updates to fix security vulnerabilities. Enable automatic updates where possible.
Worked examples
Example 1: Network recommendation (6 marks)
A company currently operates from a single office building with 45 computers. They plan to expand by opening a second office 200 miles away with 30 computers. Both offices need to share files and use the same database.
(a) Identify the network type currently used in their single office. [1]
Answer: LAN (Local Area Network)
(b) Identify the network type needed after expansion to connect both offices. [1]
Answer: WAN (Wide Area Network)
(c) Explain two advantages of connecting both offices into a network. [4]
Answer:
- Employees at both locations can access the same centralized database [1], ensuring everyone works with up-to-date information and avoiding data duplication [1]
- Files can be shared between offices without physical transfer [1], speeding up collaboration and reducing costs of couriers or travel [1]
Marking guidance: Each advantage requires identification [1] plus development/explanation [1].
Example 2: Security scenario (8 marks)
An online banking website needs to protect customer data.
(a) Describe how HTTPS protects customer data. [3]
Answer: HTTPS encrypts data [1] transmitted between the customer's browser and the bank's web server [1]. This prevents intercepted data from being read by unauthorized parties [1].
(b) Describe how two-factor authentication increases security. [3]
Answer: Requires two different authentication methods [1], for example a password (something you know) and a code sent to your mobile phone (something you have) [1]. Even if someone discovers your password, they cannot access the account without the second factor [1].
(c) Identify two threats to online banking customers. [2]
Answer:
- Phishing [1]
- Keylogging/spyware [1]
Example 3: Cloud storage comparison (6 marks)
A photographer is deciding whether to store photos on local hard drives or cloud storage.
Compare local storage and cloud storage for this purpose. [6]
Answer:
Local storage advantages: No ongoing subscription costs [1]; faster access speeds without internet dependency [1]; complete control over physical location of data [1]
Cloud storage advantages: Files accessible from any device with internet connection [1], useful when meeting clients; automatic backups prevent data loss if hard drive fails [1]; storage capacity easily increased without buying hardware [1]
Marking guidance: Must present both sides. Award marks for valid comparisons with justification for photographer's context.
Common mistakes and how to avoid them
Mistake: Confusing switches and routers — stating "a switch connects a LAN to the internet."
Correction: Switches connect devices within a single LAN using MAC addresses. Routers connect different networks together (like your LAN to the internet) using IP addresses. Remember: switch = same network; router = different networks.
Mistake: Defining a WAN as simply "a large network" without mentioning geographical separation or third-party infrastructure.
Correction: Emphasize that WANs connect geographically separated sites and use telecommunications infrastructure owned by third parties (not the organization). Size alone doesn't define a WAN.
Mistake: Drawing star topology diagrams with devices connected in a circle or showing connections between devices rather than all connecting to the central switch.
Correction: In star topology, draw the central switch clearly in the middle with straight lines radiating outward to each device. No device connects directly to another device.
Mistake: Listing antivirus advantages without explaining they need regular updates, or stating they provide "100% protection."
Correction: Antivirus software requires regular updates to detect new threats. No security measure is completely foolproof — always mention limitations. Antivirus detects "known" threats based on signature databases.
Mistake: Describing phishing as a software/virus rather than a social engineering technique.
Correction: Phishing is not malware — it's a deceptive technique using fake emails or websites to trick users into voluntarily revealing information. The user actively provides the data, unlike spyware which steals it secretly.
Mistake: Writing vague security answers like "encryption makes data secure" without explaining the conversion to unreadable format or mentioning decryption keys.
Correction: Explain that encryption converts data into coded form that appears as meaningless characters. Only someone with the correct decryption key can convert it back to the original readable format.
Exam technique for Networks and the Internet
Command word awareness: "Describe" questions (worth 2-3 marks each) require you to state a feature AND add detail or consequences. For example: "A firewall monitors incoming traffic [1] and blocks unauthorized access attempts based on security rules [1]." Single-word or brief phrase answers lose marks.
Draw accurately: Topology diagrams must be clear and precise. Use a ruler for neat lines in star topology. Label the central device as "switch" or "hub." In exam papers, poorly drawn diagrams where the topology type is unclear receive no marks.
Compare means both sides: When asked to compare (e.g., LAN vs WAN, cloud vs local storage), you must present advantages AND disadvantages or features of BOTH options. Answers discussing only one side earn maximum half marks. Use comparative language: "whereas," "in contrast," "however."
Security questions need specific threats and specific solutions: Avoid vague answers like "use security software." Name the specific type: antivirus software, firewall, encryption. Match protection methods to appropriate threats — encryption for data interception, firewall for unauthorized access, antivirus for malware.
Quick revision summary
Networks connect computers to share resources and data. LANs cover single sites; WANs connect geographically separated locations using third-party infrastructure. Star topology (all devices to central switch) is most common. Essential hardware includes NICs, switches (forward data using MAC addresses within LANs), routers (connect different networks using IP addresses), and servers. TCP/IP, HTTP/HTTPS, and FTP are key protocols. Cloud computing provides internet-based services with advantages (accessibility, scalability) and disadvantages (requires internet, ongoing costs). Security threats include viruses, phishing, and DDoS attacks. Protection requires firewalls, antivirus software, encryption, authentication, and regular updates.