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7 layer OSI Model

The Presentation Layer

:Let us take the example of an Image. We view several images on the web and I am sure you are aware that image follow several compression standards. Without compressing an Image it would take forever to download it to you browser which might account for increase in blood pressure or early greying of the hair. In the case of images the most popular are tiff and jpeg. Now imagine a web site which contains an image, when the web site is displayed on your browser the image has to be downloaded from the server where the site is hosted. If the compression standard followed in JPEG in that case the application has to be smart enough to make sense of the compressed data and display it one the screen. This is where the presentation layer of the application comes into picture.

Any application developed should take care to cater to all the standards presently existent if it wants to be popular among the masses. An internet explorer application would have an interface which reads any image data and converts it into a sensible format (a format which makes sense to the front end). The image can be in TIFF format or JPEG format, its upto the application to handle it and the application written to handle it is the property of Presentation layer. Makes sense doesn't it. So OSI has protocol standards which define how standard data should be formatted. Tasks such as encryption,decryption,compression and decompression belong to the presentation layer. Without the existence of proper standards for the above tasks (like JPEG for images,MPEG for videos are standards of data representation) the life of a software programmer would be one holy nightmare.

Continue to: OSI Session Layer