Computer Science (2210)
LAN (Local Area Network): Small area like a school or office. Usually owned by one organisation. WAN (Wide Area Network): Large area, connects LANs across cities/countries. The Internet is the biggest WAN!
Router: Directs data between networks (your home router connects you to the internet) Switch: Connects devices within a LAN, sends data to specific device NIC (Network Interface Card): Hardware in your device that connects to a network WAP (Wireless Access Point): Enables WiFi connections
Copper cables: Cheap but slow, affected by interference Fibre optic: Very fast, uses light pulses, expensive Wireless: Convenient but can be intercepted, affected by walls/distance
Internet: Global network of networks (the infrastructure) WWW: Collection of websites accessed via the internet (a service on the internet) HTTP/HTTPS: Protocols for accessing web pages (S = Secure) IP Address: Unique address for every device (e.g., 192.168.1.1) DNS: Converts domain names (google.com) to IP addresses
Star: All devices connect to central switch. If switch fails, all go down. Bus: All devices on one cable. If cable breaks, network splits.
Topic 3 of 5Cambridge O Levels
Networks & the Internet
How computers connect and communicate
A computer network is two or more computers connected together to share data and resources.
Types of Networks:
Network Hardware:
Transmission Media:
The Internet & WWW:
Network Topologies:
Key Points to Remember
- 1LAN = small area, WAN = large area. Internet = biggest WAN
- 2Router connects networks, Switch connects devices in LAN
- 3Fibre optic > Copper cables for speed
- 4DNS converts domain names to IP addresses
Pakistan Example
PTCL Fibre & 4G Networks
PTCL's fiber optic network connects Pakistani cities — light pulses travel through glass cables at near light-speed! When you open YouTube on your Jazz 4G phone: your phone connects via wireless to the nearest cell tower (WAP), which connects via fiber to Jazz's network (LAN), which connects via submarine cable (WAN) to Google's servers. DNS converts 'youtube.com' to an IP address. Data travels thousands of kilometers in milliseconds. Pakistan's 7 submarine cables landing at Karachi connect us to the global internet — if they all break, Pakistan goes offline!