Before 1990 the Open Systems Interconnection (OSI) model dominated data communications and networking. The OSI model was not fully implemented. The TCP / IP protocol suite became the dominant commercial architecture because it was used and tested extensively in the Internet.
The International Standards Organization (ISO) which was established in 23 February 1947 is a multinational body dedicated to worldwide agreement on International standards. The organization standard that covers all aspects of network communications is the OSI model which was first introduced in 1970s.
The purpose of OSI model is to shows how to facilitate communication between different systems without requiring changes to the logic of underlying hardware and software.
The OSI is a model for understanding and designing a network architecture that is flexible, robust and interoperable but not a protocol.
The OSI Model is a layered framework for the design of network systems that allows communication between all types of computer systems.
The OSI model consists of seven separate layers. Each layer defines the process of moving information across the network.
The Architecture Of OSI Model Layers
Layer 1 – The Physical Layer
Layer 2 – The Data Link Layer
Layer 3 – The Network Layer
Layer 4 – The Transport Layer
Layer 5 – The Session Layer
Layer 6 – The Presentation Layer
Layer 7 – The Application Layer
The layers involvement when a message is sent from one device to another device. As the message travels from one device to another it may pass through several intermediate nodes or devices. These intermediate nodes or devices usually involve only the first three layers of the OSI model.
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The designers of OSI model distilled the process of transmitting data to its most fundamental elements. They identified which networking functions had related uses and collected those functions into discrete groups that became the layers. Each layer defines a family of functions distinct from those of the other layers, the designers created an architecture that is both comprehensive and flexible.
The communication governed by an agreed-upon series of rules and methodology called protocols. The processes on each machine that communicates at a given layer are called peer-to-peer processes. Correspondence between machines is a peer-to-peer process using the protocols fitting to a given layer.