Computer Networks and the Internet
Computer Networks and the Internet covers how devices communicate, the hardware and protocols involved, and why network design choices matter. You should be able to compare LANs and WANs, describe packet switching, and match protocols to their purpose.
Network types and topologies
- A LAN covers a small area and is usually owned by one organisation; a WAN spans larger distances and often uses leased links.
- Star topology uses a central switch: a cable failure affects one device, but the switch is a single point of failure. Bus and ring topologies are older and have different failure characteristics.
- Client-server centralises control and backup; peer-to-peer shares directly between devices but scales less well.
Hardware and protocols
- A switch forwards frames within a LAN using MAC addresses; a router forwards packets between networks using IP addresses.
- TCP provides reliable, ordered delivery; IP handles addressing and routing. HTTP/HTTPS transfer web pages, FTP transfers files, SMTP sends email, DNS resolves domain names, and DHCP assigns IP configuration automatically.
- Packet switching splits data into packets that may travel different routes and are reassembled at the destination.
Worked example
A 60 MB file is downloaded at 20 Mbps. Convert: 60 × 8 = 480 megabits. Time = 480 ÷ 20 = 24 seconds. In practice, overheads and congestion make it slightly longer.
Traps
Do not treat the Internet and the World Wide Web as the same thing: the web is a service on the Internet. Do not say a switch routes between networks. Keep Mbps, megabits per second, separate from MB/s, and do not confuse bandwidth, which is capacity, with latency, which is delay.