This is the sixth layer in the OSI model. The objective of this layer is the provision of certain functions. Primarily, the functions of coding and conversion are used in application layer data. The main responsibility of these functions is to ensure that the information or data sent from the application layer of a certain system is logical to the application layer of another system. Presentation layer coding and conversion scheme examples include data representation formats, conversion arrangements, compression method and encryption design. Data representation formats make the use of pictures, sound and video configurations and allow for the exchange of application of data between different computer systems. In the system exchange of information which makes use of different text and data representations, such as EBCDIC or ASCII, conversion schemes are used. Whenever need occurs at the destination for decompression of data that was compressed at the source device, ordinary data compression schemes are put to use.
Some of the most common and well known compression and coding designs especially for graphic images include (GIF) Graphic Interchange Format and (JPEG) Joint Photographic Exchange Group. Also, if data was encrypted at the source device, data encryption methods can be used so that messages can be clearly interpreted. Thus, the layer is responsible for how data is arranged by a particular application before it is sent into the network. With the help of the presentation layer, an application can easily read and comprehend a particular message. Consequently, the importance of the presentation layer lies in the fact that the layer is used in message encryption and decryption primarily for protection reasons. Secondly, the presentation layers helps to compact and or expand messages at the source so that they can travel efficiently. Also, it helps the same message to be decompressed at the end.
It is also through the presentation layer that such tasks as the configuration of graphics and the transformation of message content are made possible. Again, the presentation layer makes the conversion of system particular messages possible. The External Data Representation (XDR) can be found in the presentation layer. The role of the XDR is the conversion of the local representation of data to a canonical form. Canonical data is usually independent of the host and uses a typical principle for information ordering and the grouping of structures. The layer is the link between the session and application layers. It presents data from one to the other.