📘 Study Focus | Domain 4: Communication and Network Security

📘 Domain 4: Communication and Network Security

🔑 Flashcard Topics (Protocol-Centric and Architecture-Heavy Content)

🌐 Network Models & Protocols

📶 OSI Model – Layer Functions

  • Mnemonic: All People Seem To Need Data Processing (7→1)
    7-Application, 6-Presentation, 5-Session, 4-Transport, 3-Network, 2-Data Link, 1-Physical.

🧩 Common Protocols by OSI Layer

  • Layer 7 (App): HTTP, FTP, DNS, SMTP

  • Layer 4 (Transport): TCP (reliable), UDP (fast)

  • Layer 3 (Network): IP, ICMP, IPsec

  • Layer 2 (Data Link): Ethernet, ARP, PPP

  • Layer 1 (Physical): Fiber, coax, electrical signals

📌 TCP vs UDP

  • TCP = reliable, connection-oriented, handshake (e.g., HTTPS).

  • UDP = fast, connectionless, no guarantees (e.g., VoIP, DNS).

🛡️ Secure Protocols

🔒 IPSec (Layer 3)

  • Transport Mode = Encrypts payload only (used in end-to-end).

  • Tunnel Mode = Encrypts entire packet (used in VPNs/gateways).

  • ESP vs AH
    ESP = encrypts + authenticates; AH = authenticates only.

🔐 TLS/SSL (Layer 5–7)

  • Uses X.509 certificates for encryption and authentication.

  • Handshake = asymmetric key exchange → symmetric session key

📫 Email Security Protocols

  • S/MIME = encryption + digital signature (X.509)

  • PGP = web of trust model, similar purpose

🔁 Transmission Methods & Switching

📡 Circuit Switching vs Packet Switching

  • Circuit = dedicated path (old phone lines)

  • Packet = data split into packets (Internet, VoIP)

🔃 Tunneling Protocols

  • GRE, PPTP, L2TP, IPSec
    Used to encapsulate traffic within other protocols.

🔗 Network Devices

📥 Firewalls

  • Packet-Filtering = L3/L4 rules, stateless

  • Stateful Inspection = tracks connection state

  • Proxy Firewall = inspects full packets (Layer 7)

  • Next-Gen Firewall (NGFW) = combines stateful + IDS/IPS

📡 IDS vs IPS

  • IDS = Detects and alerts, passive

  • IPS = Detects and blocks, inline

🛠️ Security Concepts

🛡️ Defense in Depth

  • Layered security across physical, technical, and administrative controls.

🚫 Network Segmentation

  • Divides network into zones; limits lateral movement of attackers.

🌐 DMZ (Demilitarized Zone)

  • Hosts public-facing services while isolating internal network.

🕳️ Common Network Attacks

  • Spoofing = Pretend to be someone else (IP, ARP, DNS)

  • Sniffing = Capture unencrypted data (packet analyzers)

  • Replay Attack = Resend valid data to gain access

  • Man-in-the-Middle (MitM) = Intercept & alter data in transit

  • DDoS = Overwhelm with traffic from many sources

This domain is highly testable, but more fact-heavy than logic-heavy, making it perfect for flashcard drilling.


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