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OSI Model vs TCP/IP Model

Comparing the OSI (Open Systems Interconnection) model and the TCP/IP (Transmission Control Protocol/Internet Protocol) model is essential to understand the fundamental differences in how these two models conceptualize network communications. Both serve as frameworks for understanding and designing network systems, but they have distinct structures and focuses.

OSI Model

1. Layers: It consists of 7 layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical.
2. Standardization: Developed by the International Organization for Standardization (ISO).
3. Approach: Highly theoretical and comprehensive, each layer is clearly distinct with specific functions.
4. Interoperability: Designed to promote interoperability between products from different manufacturers.
5. Functionality:
   • Application Layer: Network process to application.
   • Presentation Layer: Data representation and encryption.
   • Session Layer: Inter-host communication.
   • Transport Layer: End-to-end communication.
   • Network Layer: Path determination and logical addressing.
   • Data Link Layer: Physical addressing.
   • Physical Layer: Transmission and reception of raw bit streams.

TCP/IP Model

1. Layers: It has 4 layers: Application, Transport, Internet, and Link.
2. Standardization: Developed by the Defense Advanced Research Projects Agency (DARPA) for the internet.
3. Approach: More practical and based on standard protocols used on the internet.
4. Interoperability: Focused on achieving interconnectivity and establishing a global network.
5. Functionality:
   • Application Layer: Combines the application, presentation, and session layer functions of OSI.
   • Transport Layer: Same as OSI’s transport layer.
   • Internet Layer: Similar to OSI’s network layer, routing of data.
   • Link Layer: Combination of OSI’s data link and physical layers.

Key Differences

• Number of Layers: OSI has 7 layers, whereas TCP/IP has 4 layers.
• Model Design: OSI is more theoretical, whereas TCP/IP is more practical and aligned with real-world networking protocols.
• Layer Functions: Some OSI layers are combined into single layers in TCP/IP.
• Adoption: TCP/IP is the standard model used for the internet, while OSI serves more as a reference model.
• Flexibility: TCP/IP is considered more flexible and straightforward, tailored to effectively handle the transmission of data over the internet.

Both models are crucial in the field of networking, with TCP/IP being the practical framework used in the implementation of the internet and OSI serving as a comprehensive guide for understanding and teaching network communication protocols.