Computer Networks and Internet Basics
Computer Networks and Internet Basics
The exam tests network components, addressing, protocols, and how a URL becomes a page.
Networks
- A network links devices to share resources. LAN is local; WAN spans large distances; the Internet is a network of networks.
- Topologies: bus, star, ring, mesh; star is common because a single link failure affects one node.
- Devices: hub broadcasts, switch forwards by MAC address, router forwards between networks by IP address.
- Media: twisted pair, coaxial, fibre, wireless.
Protocols and addressing
- TCP is connection-oriented and reliable; UDP is connectionless and faster but unreliable.
- IP addresses identify interfaces; MAC addresses identify hardware on a LAN. IPv4 is 32-bit; IPv6 is 128-bit.
- DNS translates domain names to IP addresses. HTTP/HTTPS transfer web pages; HTTPS adds TLS encryption.
- Email uses SMTP for sending and POP3/IMAP for retrieval.
Worked example
Typing https://www.example.com/page triggers DNS resolution of www.example.com to an IP address, then the browser opens a TCP connection to port 443, performs a TLS handshake, sends an HTTP GET for /page, and renders the response. Reasoning: name resolution must precede connection; HTTPS uses port 443 by default.
Traps
- Confusing IP address with MAC address.
- Assuming UDP guarantees delivery.
- Saying the WWW and the Internet are identical; the Web is a service on the Internet.
- Mixing up SMTP (send) with POP3/IMAP (receive).
- Forgetting DNS uses port 53 and HTTP uses port 80.