OSI Model means Open System Interconnection Model. It is primarily a networking framework used in the execution of computer protocols. It was developed in 1984 by the International Organization for Standardization (IOS). The term networking refers to the interconnection of computers for the purposes of sharing information. Networking makes the use of both computer hardware and software. Thus, the OSI model is used to describe the process through which information moves from one computer software application to another software application in another computer by way of a network intermediate.
The OSI model is then regarded as the principal method for inter computer communication. The model comprises of seven layers and each layer contains particular network functions. Accordingly, control is passed on from one layer to another. During the process of moving and sharing information between networked computers, the OSI model works by dividing the computer tasks into seven smaller task groups which form the OSI layers. The layers are representative of the different stages that data passes through as it travels from one device to another in a network. For efficiency purposes, the layers are self contained. This means the tasks can then be easily and autonomously implemented. That is, each layer should independently execute the task assigned to it. With the layers being independent, it also becomes easy to update the solutions offered by the different layers without affecting the other layers.
These seven layers are: Layer 7 – Application, Layer 6 – Presentation, Layer 5 – Session, Transport – Layer 4, Network – Layer 3, Data link – Layer 2 and Layer 1 – Physical. In the OSI model, these different layers are then divided into two; the upper and the lower layers. The upper layer is concerned largely with application issues which are executed in software. The highest layer in the upper layer is application. This is the layer closest to the computer user. Still, the term upper layer is often used to refer to any layer that is above another layer in the OSI model. For instance, since the presentation layer is above the session layer it can be referred to as an upper layer. On the other hand, the lower layer is used for the purposes of handling issues that pertain to data transport. As opposed to the upper layer, the two lower most layers in the lower layer, data link and physical are implemented through the use of both hardware and software.
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