📘 Network Notes

Network – Quick Revision Sheet

Networking Notes

• Networking is the practice of connecting computers and devices to share data and resources.
• Types of Networks
  • LAN (Local Area Network) – Small area like home, office
  • MAN (Metropolitan Area Network) – City-wide network
  • WAN (Wide Area Network) – Large area like the Internet
• Basic Networking Devices
  • Router – Connects different networks
  • Switch – Connects devices within a network
  • Modem – Connects network to ISP
  • Firewall – Protects network from threats
• IP Address
  • Unique identifier for a device on a network
  • IPv4 example:

    192.168.1.1
            

  • IPv6 example:

    2001:0db8:85a3::8a2e:0370:7334
            

• Common Network Protocols
  • HTTP / HTTPS – Web communication
  • FTP – File transfer
  • SMTP – Sending emails
  • IMAP / POP3 – Receiving emails
  • DNS – Converts domain names to IP addresses
• Ports

  HTTP  : 80
  HTTPS : 443
  FTP   : 21
  SMTP  : 25
  SSH   : 22
      

• OSI Model (7 Layers)

  7. Application
  6. Presentation
  5. Session
  4. Transport
  3. Network
  2. Data Link
  1. Physical
      

• TCP vs UDP
  • TCP – Reliable, connection-oriented
  • UDP – Faster, connectionless

Network Security Notes

• Network Security refers to protecting networks, devices, and data from unauthorized access, attacks, and misuse.
• Goals of Network Security (CIA Triad)
  • Confidentiality – Data is accessible only to authorized users
  • Integrity – Data is not altered without permission
  • Availability – Systems and data are accessible when needed
• Common Network Threats
  • Malware – Viruses, worms, trojans
  • Phishing – Fake messages to steal credentials
  • Man-in-the-Middle (MITM) – Intercepting communication
  • Denial of Service (DoS / DDoS) – Overloading a system
  • Packet Sniffing – Capturing network traffic
• Firewalls
  • Filter incoming and outgoing network traffic
  • Types:
    • Packet-filtering firewall
    • Stateful firewall
    • Application-level firewall
    • Next-Generation Firewall (NGFW)
• Encryption
  • Protects data during transmission
  • Symmetric Encryption – Same key for encryption & decryption
  • Asymmetric Encryption – Public key & private key
  • Examples:

    HTTPS → TLS/SSL
    SSH   → Secure remote access
            

• Authentication Methods
  • Password-based authentication
  • Multi-Factor Authentication (MFA)
  • Biometric authentication
  • Certificate-based authentication
• IDS & IPS
  • IDS (Intrusion Detection System) – Detects attacks
  • IPS (Intrusion Prevention System) – Detects and blocks attacks
• Secure Network Practices
  • Use strong passwords and MFA
  • Keep systems and software updated
  • Segment networks (VLANs)
  • Disable unused ports and services
  • Monitor logs and traffic
• Common Secure Ports

  HTTPS : 443
  SSH   : 22
  FTPS  : 990
  SFTP  : 22