Topic 3 covers computer networks and the internet: how data is transmitted, the protocols that govern communication, and the security challenges of networked systems.
LAN: local area network (single building/campus). WAN: wide area network (geographically dispersed, e.g., the Internet). WLAN: wireless LAN using Wi-Fi. Topologies: star (central hub/switch), bus (shared backbone), mesh (each node connected to several others). Network hardware: router, switch, hub, modem, access point, NIC.
Protocol: set of rules for data communication. TCP/IP model: Application (HTTP, FTP, SMTP, DNS), Transport (TCP/UDP), Internet (IP, routing), Network Access (Ethernet, Wi-Fi). Packet switching: data split into packets, each routed independently, reassembled at destination. TCP ensures reliable delivery (acknowledgements, retransmission); UDP is faster but unreliable.
IP addressing: IPv4 (32-bit, e.g., 192.168.1.1), IPv6 (128-bit, hex notation). DNS: translates domain names to IP addresses. HTTP/HTTPS: protocols for web pages. URL structure: scheme://host:port/path. Cookies, sessions, and web application architecture (client-server model).
Threats: malware (viruses, worms, ransomware), phishing, DDoS, man-in-the-middle attacks. Countermeasures: firewalls, encryption (symmetric, asymmetric/public-key), SSL/TLS for HTTPS, VPN, access control. Authentication: passwords, two-factor authentication, biometrics. Ethical issues: privacy, surveillance, data protection laws.
You need to understand the purpose and basic operation of key protocols (TCP, UDP, IP, HTTP, FTP, SMTP, DNS) but not the technical details of packet headers or handshake sequences. Focus on: what each protocol does, when it is used, and the difference between connection-oriented (TCP) and connectionless (UDP) communication. The OSI/TCP-IP model is tested conceptually — know which layer does what, not detailed specifications.
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