Computer Networks and Internet Basics
Computer Networks and Internet Basics
This domain covers network types, topologies, devices, addressing and core Internet services. Expect matching questions: which device or protocol performs which job.
Core rules
- A LAN covers a room or building; a MAN covers a city; a WAN covers a country or larger area. The Internet is a network of networks.
- Topologies include bus (one backbone), star (central switch or hub), ring (closed loop) and mesh (many redundant links). Star is common in laboratories because one cable fault affects only one node.
- A hub broadcasts to all ports; a switch forwards by MAC address; a router forwards between networks by IP address. A modem converts signals for the ISP link.
- TCP/IP is the Internet protocol suite. IP addresses identify interfaces; DNS translates domain names to IP addresses; HTTP and HTTPS transfer web pages.
- A URL contains a scheme, host and path, for example https://school.edu/results. Email needs an address, subject and message; attachments travel with the message.
- Bandwidth is capacity; latency is delay. They are not the same measure.
Worked example
A school laboratory has 20 PCs, one switch, one router and a broadband modem. Each PC connects to the switch; the switch connects to the router; the router connects to the modem and ISP. The switch handles local traffic using MAC addresses; the router gives the laboratory a path to the Internet using IP addresses. If one PC cable fails, star topology keeps the other 19 working.
Traps
- Calling a hub intelligent is wrong: it does not learn MAC addresses.
- Confusing an IP address with a domain name; DNS resolves the latter.
- The Internet is the infrastructure; the World Wide Web is a service on it.
- A URL is not an email address, even when both contain dots.
- Wi-Fi is a wireless LAN technology, not a WAN.
- A switch does not choose the best path between different networks; a router does.