What is a Network?

A network connects two or more computers/devices to share resources.

  • LAN (Local Area Network) – Small area like a home or office

  • WAN (Wide Area Network) – Larger area, like the internet

  • MAN (Metropolitan Area Network) – City-wide networks

  • PAN (Personal Area Network) – Bluetooth devices

7.2 Network Devices

  • Router: Connects different networks and routes traffic

  • Switch: Connects devices in a LAN

  • Hub: Basic device, sends data to all ports

  • Modem: Modulates and demodulates internet signals

  • Access Point: Provides wireless connectivity

7.3 OSI Model (7 Layers)

  1. Physical – Hardware (cables, switches)

  2. Data Link – MAC addresses, Ethernet

  3. Network – IP addresses, routing

  4. Transport – TCP, UDP (ensures data delivery)

  5. Session – Manages connections

  6. Presentation – Data translation and encryption

  7. Application – Interface for applications (HTTP, FTP)

7.4 TCP/IP Model (4 Layers)

  • Application, Transport, Internet, Network Access

  • Protocols: HTTP, HTTPS, DNS, DHCP, FTP

7.5 IP Addressing

  • IPv4: e.g., 192.168.1.1

  • IPv6: e.g., 2001:0db8::1

  • Subnetting divides networks for security and performance.

7.6 Ports and Protocols

  • Port 80: HTTP

  • Port 443: HTTPS

  • Port 21: FTP

  • Port 25: SMTP (email)

7.7 Network Troubleshooting Tools

  • ping – Test connectivity

  • tracert / traceroute – Show route to a destination

  • ipconfig / ifconfig – View network settings

  • nslookup – Check DNS resolution