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
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.
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.