AL ICT Lesson 6: Networking (දත්ත සන්නිවේදනය හා ජාලකරණය)

Guided media: data travels along a physical path (e.g. twisted pair, coaxial cable, fibre optics).
Unguided media: data travels through the atmosphere as electromagnetic waves (e.g. radio waves, microwaves, infrared).
Signal properties: amplitude, frequency, phase and bandwidth.
Signal impairments: attenuation (loss of strength), noise (unwanted added energy) and distortion.

A/L ICT Lesson 06: Data Communication & Networking

Bilingual, exam-focused notes for Unit 6 of the Sri Lankan GCE Advanced Level ICT syllabus (Grade 12), covering data communication and computer networking. The lesson explains transmission media (guided and unguided) and signal impairments such as attenuation and noise, network topologies (star, bus, ring and mesh), IP addressing and subnetting for IPv4, and the OSI and TCP/IP reference models with key protocols including TCP, UDP, IP, DNS and DHCP. It also covers network devices (router, switch, hub, repeater, gateway), the client/server model, LAN versus WAN, encryption (symmetric and asymmetric) and VPNs. Includes an interactive subnet calculator, structured A/L essay questions with model answers, fifteen five-option MCQs with explanations, and bilingual flashcards.