Show understanding of the characteristics of a LAN (local area network) and a WAN (wide area network)

Published by Patrick Mutisya · 14 days ago

Cambridge A-Level Computer Science 9618 – Networks: LAN vs WAN

2.1 Networks – The Internet

Objective

Show understanding of the characteristics of a LAN (Local Area Network) and a WAN (Wide Area Network).

Key Definitions

  • LAN (Local Area Network): A network that interconnects devices within a limited geographical area such as a home, office, or campus.

  • WAN (Wide Area Network): A network that spans a large geographical area, linking multiple LANs, cities, or even countries.

Characteristic Comparison

CharacteristicLANWAN
Geographical ScopeTypically < 10 km (e.g., a building or campus)Hundreds to thousands of kilometres; can be global
OwnershipUsually owned and managed by a single organisationOften a combination of private and public providers; shared infrastructure
Transmission MediaEthernet (copper or fibre), Wi‑Fi, coaxial cableLeased lines, satellite links, MPLS, public Internet, fibre optic backbone
Typical Data Rates10 Mbps – 10 Gbps (Ethernet standards)1 Mbps – 100 Gbps (depending on technology and provider)
LatencyLow (typically < 1 ms)Higher (tens to hundreds of ms) due to distance and routing
TopologyStar, bus, ring, or mesh (often star with a central switch)Complex hierarchical or mesh structures; often based on ISP backbone topology
Security ControlsFirewalls, VLANs, MAC filtering, WPA2/WPA3 for Wi‑FiVPNs, IPSec tunnels, firewalls at edge routers, encryption of data in transit
Typical DevicesSwitches, routers, wireless access points, PCs, printers, serversCore routers, edge routers, WAN optimisers, satellite dishes, modems
CostRelatively low – equipment and cabling are inexpensive for small areasHigher – leasing lines, satellite bandwidth, and maintenance are costly

Performance Metrics

When evaluating LANs and WANs, the following metrics are commonly used:

  1. Bandwidth – maximum data transfer rate, measured in bits per second (bps).

  2. Latency – time for a packet to travel from source to destination, measured in milliseconds (ms).

  3. Jitter – variation in latency, important for real‑time applications.

  4. Packet loss – percentage of packets that never reach the destination.

Example Calculations

Suppose a LAN provides a bandwidth of 1 Gbps and a WAN link provides 100 Mbps. If a file of size 500 MB needs to be transferred:

\$\text{Transfer time}_{\text{LAN}} = \frac{500 \times 8 \text{ Mb}}{1000 \text{ Mb/s}} = 4 \text{ s}\$

\$\text{Transfer time}_{\text{WAN}} = \frac{500 \times 8 \text{ Mb}}{100 \text{ Mb/s}} = 40 \text{ s}\$

This illustrates how bandwidth directly influences transfer speed, while latency would affect interactive applications such as video conferencing.

Typical Use‑Cases

  • LAN: Office file sharing, local printing, internal email servers, gaming LAN parties.

  • WAN: Connecting branch offices, accessing cloud services, inter‑university research networks, global e‑commerce platforms.

Suggested diagram: A schematic showing a LAN (with switches, PCs, Wi‑Fi) connected via a router to a WAN (multiple remote sites, ISP backbone, satellite link).

Summary

A LAN is characterised by its limited geographic scope, high speed, low latency, and ownership by a single entity. A WAN covers much larger distances, often relies on third‑party infrastructure, and exhibits higher latency and cost. Understanding these differences helps in designing appropriate network solutions for specific organisational needs.