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What Is the OSI (Open Systems Interconnection) Model?

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OSI Model - upper and lower layers

Layers of the OSI Model

Definition: The OSI model defines internetworking in terms of a vertical stack of seven layers. Upper layers of the OSI model represent software that implements network services like encryption and connection management. Lower layers of the OSI model implement more primitive, hardware-oriented functions like routing, addressing, and flow control.

Data communication in the OSI model starts with the top layer of the stack at the sending side, travels down the stack to the sender's lowest (bottom) layer, then traverses the physical network connection to the bottom layer on the receiving side, and up its OSI model stack.

The OSI model was introduced in 1984. Designed to be an abstract model and teaching tool, the OSI model remains a useful for learning about today's popular network technologies like Ethernet and protocols like IP.

More - How Computer Networks Work - Introduction to Protocols

Also Known As: Open Systems Interconnection (OSI) reference model, OSI seven layer model
Examples:
Internet Protocol (IP) corresponds to the Network layer of the OSI model, layer three. TCP and UDP correspond to OSI model layer four, the Transport layer. Lower layers of the OSI model are represented by technologies like Ethernet. Higher layers of the OSI model are represented by application protocols like TCP and UDP.

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