The Open System Interconnection (OSI) model was developed by International Organisation of Standardisation (ISO) in 1984 to conceptualise the working of a networking system. In networking, when we send data, it goes through various steps at the back-end to make the communication successful, and through its 7 layers, the OSI model helps us to understand how that information travelled over a network. It not only helps the users to comprehend the process but also guides the manufacturers so that they can develop products that can inter-operate with the products developed by other vendors. Hence, we can say that an OSI model is the backbone of a network.
The purpose of networking is to enable communication between various devices interconnected over a network and the OSI model caters to that need. What a user sees as a result on the screen is due to the working of the service layer of the OSI model which includes the layer 7 – Application, and layer 6 – Presentation. It ensures that the data is in a usable form and this is the layer where data encryption occurs. The middle layer of the OSI contains the layer 5 – Session layer, which maintains the connections and is responsible for controlling ports and sessions, and layer 4 – Transport layer, which uses transmission protocols, like TCP/IP, to transmit data enable end-to-end communication. The operating system layer also has two layers functioning – layer 3, Network layer, which is responsible for the logical addressing (Ipv4 or IPv6) of the data (called packet at this layer), and layer 2, Data-link layer, which transforms the packets into frames by adding physical addressing (MAC address) to the packets. Finally, layer 1 – Physical layer – sends the data over the physical medium in the form of bits. Some new concepts these days are also named based on the OSI model, for example, Layer 2 Tunnelling Protocol.
OSI model standardises the entire networking process. It is the best guiding covenant for the vendors, the best learning tool for the students, and even helps a network designer by giving an idea about the type, and number, of hardware and software required to set up a sustainable network. As it breaks the complex process into smaller and simpler components, it makes troubleshooting quick and efficient as well. We can say, the entire networking depends upon the proper functioning of all the layers of the OSI model.
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