Computer Networks, Data Communication and the Internet
Domain focus
Network questions cover network types and topologies, transmission media, devices, protocols and internet services.
Core rules
- LAN covers a small area such as a school; WAN covers a large geographical area; PAN is personal; MAN is city-wide.
- Topologies: star uses a central switch/hub; bus shares one backbone; ring passes data around a loop; mesh offers multiple paths.
- Media: twisted-pair copper, coaxial cable, fibre-optic (high bandwidth, immune to electrical interference) and wireless (radio, microwave).
- Devices: a hub broadcasts to all ports; a switch forwards frames using MAC addresses; a router connects networks and routes using IP addresses; a modem converts signals for a line.
- Protocols: TCP/IP for internet communication; HTTP/HTTPS for web pages; FTP for file transfer; SMTP for sending email; DNS translates domain names to IP addresses.
- The internet is the global network of networks; the World Wide Web is a service of linked pages on it. A URL identifies a resource; a browser displays it; an ISP provides access.
- Client-server centralises control; peer-to-peer shares directly between devices.
Worked example
A school lab needs to share files and one printer, with central control and internet access. Recommend a network type, topology and device. Reasoning: a LAN fits one site. A star topology with a switch gives central connection and easy fault isolation; a server provides central file and account control (client-server). A router connects the LAN to the ISP for internet access.
Traps
- Treating the internet and the World Wide Web as identical.
- Saying a hub intelligently forwards to one device; it broadcasts.
- Confusing a router with a switch.
- Using HTTP for email.
- Naming an IP address as a physical hardware address; that is the MAC address.