OSI Explain
The Open Systems Interconnection (OSI) Model Explained
The OSI model (Open Systems Interconnection) is the fundamental conceptual framework used to understand network communication. It standardises the functions of a communication system into seven distinct layers, helping students, network engineers, and IT professionals troubleshoot and design networks effectively.
From physical cables to the web browser you're using right now, the 7 layers of the OSI model work together to make the internet possible. This interactive guide provides a deep dive into each layer with protocol examples, Wireshark captures, and real-world analogies.
Click on any layer below to access detailed explanations, protocol examples, interactive demonstrations, and teaching materials for that specific layer.
Memory Aids
Bottom → Top (Layer 1 to 7):
Physical · Data Link · Network · Transport · Session · Presentation · Application
Top → Bottom (Layer 7 to 1):
Application · Presentation · Session · Transport · Network · Data Link · Physical
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Where to go next
One HTTPS request, step by step: every header added on the way down, changed by routers in the middle, and removed on the way up.
Mixed questions across all seven layers, with an explanation after every answer. Good preparation for CompTIA Network+ and CCNA.
See how the seven theoretical layers map onto the four layers that actually run the internet, with PDU names side by side.
Over 140 terms — MAC, MTU, MSS, ARP, NAT, sliding window and more — each tagged with the layer it belongs to. Study them as flashcards, one layer at a time.
Each layer page ends with a link to the next, so you can walk the whole stack from cables to HTTP in one sitting.
Frequently Asked Questions (FAQ)
The Open Systems Interconnection (OSI) model is a conceptual framework that divides network communications into seven layers. It helps standardise networking functions to support interoperability between different products and software.
The 7 layers are: 1. Physical, 2. Data Link, 3. Network, 4. Transport, 5. Session, 6. Presentation, and 7. Application. A common memory aid is "Please Do Not Throw Sausage Pizza Away".
It provides a universal language for networking professionals, aids in troubleshooting by isolating issues to specific layers, and helps vendors create interoperable hardware and software.
The OSI model is a theoretical framework with 7 layers, while TCP/IP is the practical model used for the Internet with 4 layers. OSI is better for understanding concepts, while TCP/IP reflects real-world implementation.