Computer Networks and the Internet
Domain focus
Computer Networks and the Internet tests topologies, network devices, addressing, protocols and Internet services. Questions often ask you to choose a device for a scenario or explain why a network is slow or insecure.
Core rules and concepts
- LAN covers a small area; WAN spans large distances; the Internet is a global network of networks.
- Star topology uses a central switch; a cable failure affects one device, but the central device is a single point of failure. Bus shares one backbone; mesh gives redundancy at higher cost.
- Hub repeats signals to all ports; switch forwards frames by MAC address; router forwards packets between networks; modem converts signals for an ISP; access point connects wireless clients.
- IP address identifies a device; DNS resolves names to IP addresses; DHCP assigns addresses automatically.
- HTTP and HTTPS, SMTP, FTP and IMAP are application protocols. HTTPS adds encryption.
- Bandwidth is capacity; latency is delay. More bandwidth does not remove high latency.
Worked example
A small office has eight computers, one printer and Internet access. Use a switch to connect the wired computers and printer, a router to connect the LAN to the ISP, and a wireless access point for laptops and phones. The router’s DHCP service issues private IP addresses; DNS lets users type a domain name instead of a numeric address. If staff complain that web pages load slowly but local printing is fast, the likely bottleneck is the Internet link or latency, not the LAN switch.
Traps that cost marks
Confusing a router with a modem; saying a hub is smarter than a switch; mixing up DNS and DHCP; treating bandwidth as the same as speed; assuming HTTPS encrypts the whole computer; and forgetting that a star network depends on its central device.