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Commonly confused · Networking Fundamentals

OSI Model vs TCP/IP Model: What's the Difference?

The OSI model is a seven-layer conceptual reference used to teach and troubleshoot networking, while the TCP/IP model is the four-layer model the Internet protocols were actually built on. TCP/IP merges OSI's top three layers into one Application layer and its bottom two into one Link (Network Access) layer.

vs

TCP/IP Model

Full definition
OSI ModelTCP/IP Model
Number of layers74 (some texts use a 5-layer variant)
Layer namesPhysical, Data Link, Network, Transport, Session, Presentation, ApplicationLink/Network Access, Internet, Transport, Application
OriginISO reference modelDoD/ARPANET protocol suite
PurposeTeaching and troubleshooting referencePractical implementation of Internet protocols
Upper layersSession, Presentation, Application kept separateCombined into a single Application layer
Mapping exampleIP at Layer 3 (Network)IP at the Internet layer
Remember it

OSI has seven layers to learn; TCP/IP has four layers that actually run the Internet.

Exam tip

Questions often name a protocol or device and ask its OSI layer, or ask which TCP/IP layer corresponds to an OSI layer. Memorize that OSI Layers 5-7 map to TCP/IP Application and Layers 1-2 map to Link.

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