Four layered TCP/IP model had only a single layer (Network Access Layer) to define the functionalities for lower level data transmission (similar to functions associated with Physical layer and Datalink layer of OSI model).The functionalities of top three layers of OSI reference model (Application Layer, Presentation Layer and Session Layer) are merged to a single layer, called as "Application Layer" in both five layered TCP/IP model and original four layered TCP/IP model.The apparent differences between original four layered TCP/IP model and five layered TCP/IP model are listed below. Please refer below image, which shows a comparison between seven layered OSI reference model and five layered TCP/IP model. Please refer below image, which shows five layered TCP/IP model. I believe that, five layered TCP/IP model was introduced to match the layers and functions of TCP/IP model and OSI model together. So, the Transport Layer is Layer 4 of OSI model, but it is shown as Layer 3 of original four layered TCP/IP model. Even though OSI model has a Transport Layer, that resides in Layer 4 of OSI model. If we use the terms Layer 2 and Layer 3 related with original four layered TCP/IP model for reference instead of seven layered OSI reference model, everything will become meaningless.įor example, in OSI reference model, Layer 3 is Network layer, but in four layered TCP/IP model Layer 3 is Transport Layer. The functions of layers in original four layered TCP/IP model are different than in that of seven layered OSI model. Refer below image, which shows a comparison between seven layered OSI model and original four layered TCP/IP model. Those technical terms became the core technical reference terms in networking.
Switching and MAC addresses are the functions of Layer 2 (Datalink Layer) of OSI model. Over decades, many terms related with OSI model became the core technical reference terms related with computer networking.įor example - Routing and IP addresses are the functions of Layer 3 (Network Layer) of OSI model. Seven layered OSI model was used as a reference model for teaching computer networking and explain networking concepts for decades. We also have an updated five layered TCP/IP model, which is almost similar to seven layered OSI reference model.
We have learned about seven layered OSI reference model and four layered TCP/IP model in previous lessons.
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