Computer Networks and Internet Concepts
What this domain tests
Data communication and internet basics: network types and topologies, transmission media, OSI and TCP/IP layers, IP addressing, and the client–server protocols behind the web and email.
Core rules
- LAN is local and privately owned; WAN spans large distances; MAN covers a city. Topologies include bus, star, ring, mesh, tree and hybrid. Star is easy to fault-isolate but depends on the central hub or switch; mesh gives redundancy at high cabling cost.
- Guided media: twisted pair, coaxial, fibre optic (highest bandwidth, immune to electromagnetic interference). Unguided: radio, microwave, infrared.
- OSI has seven layers: Physical, Data Link, Network, Transport, Session, Presentation, Application. TCP/IP has four: Network Access, Internet, Transport, Application.
- IPv4 is 32-bit; IPv6 is 128-bit. Classes A–C are unicast, D multicast, E reserved. Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
- DNS resolves names to IP addresses. HTTP uses port 80, HTTPS 443, SMTP 25 for sending mail, POP3 110 and IMAP 143 for retrieving it.
Worked example
Classify 192.168.10.5. The first octet 192 lies in 192–223, so it is Class C with default mask 255.255.255.0. Because it falls in 192.168.0.0/16, it is a private address and is not routed on the public internet.
Traps that cost marks
Confusing MAC (Data Link, 48-bit hardware address) with IP (Network, logical address); saying HTTPS uses port 80; mixing up SMTP and POP3 direction; treating a hub as a switch (a hub broadcasts to all ports); misclassifying 127.x.x.x, which is loopback rather than a usable Class A address.