A2.1.1 Describe the purpose and characteristics of networks.
• Networks: local area network (LAN), wide area network (WAN), personal area network (PAN), virtual private network (VPN)
The big idea
Computer networks are engineered systems that interconnect digital devices so they can exchange data and share resources efficiently and securely. By abstracting distance and hardware differences, a network turns many separate computers into a single cooperative platform.
Purposes and key characteristics of the four syllabus network types
| Network type | Principal purpose | Typical geographic scope | Ownership & administration | Technical traits | Example scenario |
|---|---|---|---|---|---|
| Local Area Network (LAN) | Share high-speed data and peripherals among devices in the same physical location | Single room, floor, building or campus (≈ 10 m – 1 km) | Usually private (enterprise, school, home) | Ethernet or Wi-Fi; ≤ 10 Gb/s; low latency; limited propagation errors; easy to extend | School lab PCs, printers, NAS on one switch |
| Wide Area Network (WAN) | Link LANs over large distances to support inter-site operations | City-to-global (≥ 10 km up to trans-continental) | Often shared carrier services (leased fibre, MPLS, Internet) plus customer routers | Heterogeneous media; lower throughput/higher latency than LAN; uses routing & QoS; diverse topologies | A multinational’s London, Singapore and NYC offices linked via MPLS backbone |
| Personal Area Network (PAN) | Connect an individual’s personal devices for data/voice transfer without cables | Within a few metres of a person (≈ 1 – 10 m) | Individual user; ad-hoc setup | Low-power radios (Bluetooth, Zigbee, NFC, UWB); ≤ 2 Mb/s (classic BT) to 480 Mb/s (UWB); battery-optimised | Smartphone tethered to wireless earbuds and smartwatch |
| Virtual Private Network (VPN) | Provide logical, encrypted tunnels across an untrusted network to emulate a private link | Overlays existing LAN/WAN/Internet; geographic scope = underlying transport | Logical network; security policy enforced by organisation | Encryption (IPsec, SSL/TLS); authentication; encapsulation; may use split-tunnelling; adds overhead & latency | Remote employee securely accesses the company LAN via IPsec tunnel over home Internet |
Putting it together
- Purpose
All four network forms exist to extend communication reach while honouring boundaries of distance, ownership or security:- LANs optimise speed and manageability on-site.
- WANs overcome geography with carrier infrastructure.
- PANs emphasise convenience and mobility at body range.
- VPNs overlay cryptography and tunnelling on any underlying transport to preserve privacy and integrity.
- Characteristics
They differ in scale, media, data rate, latency, security model and administrative control, which drive design decisions such as cabling versus radio, switching versus routing, or clear-text versus encrypted payloads.
Understanding these distinctions lets a computer scientist select or design the right network architecture for a given technical and organisational context, and to articulate that choice in the level of detail the command term Describe demands.