Open Systems Interconnection

Different communication requirements necessitate different network solutions, and these different network protocols can create significant problems of compatibility when networks are interconnected with one another. In order to overcome some of these interconnection problems, the open systems interconnection (OSI) was approved in 1983 as an international standard for communications architecture by the International Organization for Standardization (ISO) and the International Telegraph and Telephone Consultative Committee (CCITT). The OSI model, as shown in the figure, consists of seven layers, each of which is selected to perform a well-defined function at a different level of abstraction. The bottom three layers provide for the timely and correct transfer of data, and the top four ensure that arriving data are recognizable and useful. While all seven layers are usually necessary at each user location, only the bottom three are normally employed at a network node, since nodes are concerned only with timely and correct data transfer from point to point.

The application layer is difficult to generalize, since its content is specific to each user. For example, distributed databases used in the banking and airline industries require several access and security issues to be solved at this level. Network transparency (making the physical distribution of resources irrelevant to the human user) also is handled at this level. The presentation layer, on the other hand, performs functions that are requested sufficiently often that a general solution is warranted. These functions are often placed in a software library that is accessible by several users running different applications. Examples are text conversion, data compression, and data encryption.

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Comments

  1. The OSI (Open System Interconnection) 7-layer reference model characterizes an idea of moving data between arranged PCs. It depicts how data streams from one end-client application through a system into another application. This model, SEO company dubai is viewed as the essential structural model for between PC correspondence.

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  2. OSI model isn't outdated. In the TCP/IP model of the Internet, conventions are intentionally not as inflexibly planned into exacting layers as in the OSI model. RFC 3439 contains an area entitled "Layering thought about unsafe." However, TCP/IP recognizes four expansive layers of usefulness which are gotten from the working extent of their contained conventions, in particular the extent of the product application, cheap website design Dubai the start to finish transport association, the internetworking territory, and the extent of the immediate connects to different hubs on the neighborhood arrange.

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