Know and understand the differences and similarities between an extranet, intranet and the internet
4. Networks and the Effects of Using Them
Objective
Know and understand the differences and similarities between an extranet, intranet and the Internet, and be able to describe the key network devices, topologies, IP concepts, wireless technologies, cloud services, network types, performance metrics, security issues and electronic‑conferencing tools required by the Cambridge IGCSE ICT (0417) syllabus.
Key Definitions
- Internet – The worldwide public network that interconnects millions of private, academic, business and government networks. It uses the TCP/IP protocol suite and is accessible to anyone with an appropriate connection.
- Intranet – A private network that uses the same protocols as the Internet (TCP/IP, HTTP/HTTPS, DNS) but is restricted to members of an organisation. It supports internal communication, document sharing and business applications.
- Extranet – A controlled extension of an intranet that gives selected external users (partners, suppliers, customers) limited access to specific resources. Access is secured by VPNs, firewalls and strong authentication.
Network Devices
These are the building blocks of any LAN, WLAN or WAN.
- Network Interface Card (NIC) – Provides the physical link between a computer and a network (wired or wireless).
- Hub – Layer 1 device that repeats incoming signals to all ports; creates a single collision domain.
- Switch – Layer 2 device that forwards frames only to the destination port; each port has its own collision domain.
- Bridge – Layer 2 device that connects two LAN segments and filters traffic by MAC address.
- Router – Layer 3 device that forwards packets between different networks (e.g., LAN ↔ WAN) and performs IP addressing and routing.
- Firewall – Can be hardware, software or a combination; inspects traffic and applies rules (packet‑filtering, stateful inspection, DMZ creation) to protect the internal network from unauthorised access.
Network Topologies
Understanding the physical layout helps to predict performance and fault tolerance.
- Star – All devices connect to a central switch or hub; easy to manage, a single cable failure isolates only one device.
- Bus – All devices share a single backbone cable; simple but a break in the backbone disables the whole network.
- Mesh – Devices are interconnected with multiple paths; high reliability but expensive and complex.
Basic IP Addressing
- IP addresses are written as four octets (e.g.,
192.168.12.45). - Public IP – Unique on the Internet; assigned by an ISP.
- Private IP – Used inside organisations; not routable on the public Internet. Common ranges:
10.0.0.0 – 10.255.255.255,172.16.0.0 – 172.31.255.255,192.168.0.0 – 192.168.255.255. - Subnet mask (e.g.,
255.255.255.0) determines which part of the address identifies the network and which part identifies the host.
Core Network Services
- DNS (Domain Name System) – Translates human‑readable domain names (e.g.,
www.bbc.co.uk) into IP addresses. - DHCP (Dynamic Host Configuration Protocol) – Automatically assigns IP addresses, subnet masks, gateways and DNS servers to devices on a network.
- File/Print Services – Centralised servers that store files and manage printers for LAN users.
Wireless Technologies
- Wi‑Fi (WLAN) – Based on IEEE 802.11 standards (a/b/g/n/ac/ax). Used in schools, homes and cafés.
Security: WPA2‑Personal (PSK) for small networks; WPA2‑Enterprise (or WPA3‑Enterprise) with 802.1X authentication for larger organisations.
- Bluetooth – IEEE 802.15.1, short‑range (≤10 m) for peripherals (headsets, keyboards, mice). Security relies on pairing codes and device authentication.
Cloud Computing
Services delivered over the Internet, accessed through a web browser or thin client.
- Cloud Storage – Files are stored on remote servers (e.g., Google Drive, OneDrive, Dropbox). Users upload, download and share documents.
- Software‑as‑a‑Service (SaaS) – Complete applications run on the provider’s servers (e.g., Google Workspace, Microsoft 365, Salesforce). Users interact via a browser; no local installation required.
- Advantages – Low upfront hardware cost, easy scalability, access from any device with Internet.
- Disadvantages – Dependence on Internet connectivity, ongoing subscription fees, data‑security and data‑sovereignty concerns (organisation must know where the data is physically stored).
Network Types
| Network Type | Typical Scale | Common Uses | Examples |
|---|---|---|---|
| Local Area Network (LAN) | |||
| LAN | Single building or campus | File sharing, printers, internal web sites | School computer lab, office floor |
| Wireless LAN (WLAN) | |||
| WLAN | Same as LAN but uses Wi‑Fi | Mobile device access, flexible seating | School Wi‑Fi, coffee‑shop hotspot |
| Wide Area Network (WAN) | |||
| WAN | Geographically dispersed sites | Connect multiple branches, remote access | Company offices in different cities, Internet |
| LAN‑WAN Link | |||
| LAN‑WAN link | LAN connected to a WAN via a router | Enable Internet access, inter‑site communication | School LAN ↔ ISP router ↔ Internet |
Network Performance Metrics
- Bandwidth – Maximum amount of data that can be transferred per second (measured in Mbps or Gbps).
- Latency – Time taken for a packet to travel from source to destination (measured in milliseconds).
- Jitter – Variation in latency; important for real‑time applications such as video conferencing.
Security Considerations
Security measures differ for Internet, Intranet and Extranet, but the underlying principles are the same.
- Authentication – Strong, unique passwords; two‑factor authentication (2FA); for Wi‑Fi, WPA2‑Enterprise/802.1X.
- Encryption – SSL/TLS (HTTPS) for web traffic; VPNs for remote or extranet connections; WPA2/WPA3 for wireless.
- Anti‑malware – Reputable antivirus/anti‑spyware on all devices; keep signatures up to date.
- Firewalls – Hardware firewalls at network edges; host‑based firewalls on individual computers; can create a DMZ for public services.
- VPN (Virtual Private Network) – Creates an encrypted tunnel for remote users or extranet partners.
- e‑Safety – Awareness of phishing, social engineering, safe browsing habits and reporting suspicious activity.
Good‑Practice Checklist (Student Level)
- Use a password manager to generate and store complex passwords.
- Enable automatic updates for the operating system and applications.
- Connect to Wi‑Fi only if it uses WPA2‑Personal, WPA2‑Enterprise or WPA3.
- Never share login details with anyone outside the authorised group.
- Log out of cloud services when finished, especially on shared computers.
- Report any suspicious email or link to a teacher/IT staff immediately.
Electronic Conferencing
- Video conferencing – Real‑time two‑way video and audio (e.g., Zoom, Microsoft Teams). Requires webcam, microphone and stable Internet.
- Audio conferencing – Voice‑only calls, often via telephone or VoIP (e.g., Skype, Google Meet audio‑only).
- Web‑conferencing – Shared screen, whiteboard, chat and file sharing within a browser (e.g., Google Meet, Cisco Webex).
- Classroom example – A virtual lesson where the teacher shares a PowerPoint, students ask questions via chat, and the session is recorded for later review.
Comparison of Internet, Intranet and Extranet
| Feature | Internet | Intranet | Extranet |
|---|---|---|---|
| Scope of users | Public – anyone worldwide | Private – employees and authorised internal staff | Restricted – internal staff plus selected external parties (partners, suppliers, customers) |
| Access control | None at network level – security is site‑specific (HTTPS, firewalls on individual servers) | Strong – firewalls, authentication, internal security policies | Strong – VPN, firewalls, user‑level permissions, often a separate DMZ zone |
| Typical uses | Web browsing, email, social media, cloud services, public information | Internal portals, HR systems, file servers, internal email, intranet news | Supplier portals, customer support sites, joint project workspaces, B2B applications |
| Network infrastructure | Public service providers, backbone routers, DNS root servers | Organisation’s LAN/WAN, internal routers, private DNS, dedicated firewall | Organisation’s LAN/WAN plus secure gateway (VPN concentrator, DMZ, external firewalls) |
| Security concerns | High – exposure to malware, phishing, DDoS attacks | Medium – insider threats, accidental data loss, internal malware spread | Medium‑high – must protect internal data while allowing external access; risk of mis‑configured permissions |
| Cost of implementation | Low for end‑user (subscription); high for ISPs and backbone providers | Moderate – hardware, software licences, maintenance, staff training | Higher – additional security devices, VPN licences, monitoring tools, higher maintenance overhead |
Similarities
- All rely on the same core protocols (TCP/IP, HTTP/HTTPS, DNS).
- Data is transmitted in packets through routers and switches.
- Encryption (SSL/TLS) can be applied to any of them.
- Each can host web‑based applications and services.
Advantages and Disadvantages
| Network Type | Advantages | Disadvantages |
|---|---|---|
| Internet |
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| Intranet |
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| Extranet |
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Key Points to Remember
- Internet, intranet and extranet all use the same core technologies but differ in scope, access control and security requirements.
- An intranet is completely internal; an extranet is a controlled bridge between internal and selected external users.
- Effective use of an extranet requires robust authentication, encryption (VPN/SSL) and regular monitoring.
- Choosing the right network type depends on the organisation’s need for openness versus control, cost considerations and security policies.
