Computer Communication, Networking and the Internet
Computer Communication, Networking and the Internet tests network types, topologies, transmission media, protocols, addressing and Internet services.
Core rules
Networks are classified by scale: LAN, MAN and WAN. Topologies include bus, star, ring, mesh and tree; star is common because a single cable fault affects one node, while mesh offers redundancy at higher cost. Transmission media are guided (twisted pair, coaxial, fibre optic) or unguided (radio, microwave, infrared). The OSI model has seven layers: physical, data link, network, transport, session, presentation and application. TCP/IP is the practical Internet suite. TCP is connection-oriented and reliable; UDP is connectionless. IP addresses identify hosts; IPv4 is 32-bit and IPv6 is 128-bit. DNS maps names to IP addresses; HTTP/HTTPS transfers web pages; SMTP sends mail; POP3/IMAP retrieves mail. A URL includes protocol, domain and path.
Worked example
Is 192.168.10.5 a public or private address? The first octet 192 lies in 192–223, so it is Class C. The block 192.168.0.0–192.168.255.255 is reserved for private networks. Therefore it is a private Class C address, not routable on the public Internet without NAT.
Traps
A hub broadcasts to all ports; a switch forwards by MAC address. TCP is not faster than UDP in general; it adds reliability. The OSI transport layer is not the network layer. 127.0.0.1 is loopback, not a public address. Do not confuse SMTP (sending) with POP3/IMAP (receiving).