What is the role of Presentation layer in OSI model

The presentation layer provides services to ensure that the information is protected during the transfer process. If a change is required, it is possible to select a compatible transfer syntax based on the application layer syntax. The layer converts character representation formats, which may be necessary to ensure reliable transmission. The voice coding schemes are specified at this layer. Additionally, compression and encryption are possible at this layer.

Abstract Syntax Notation 1 (ASN.1), for instance, is an example of a specification that operates at the presentation layer. A good example of how the presentation layer handles data formatting is how text is formatted.

It is possible that some applications may format text using American Standard Code for Information Interchange (ASCII), while others may use Extended Binary Coded Decimal Interchange Code (EBCDIC). Presentation layer is responsible for formatting text (or other types of data, such as multimedia or graphics files) in a way that is compatible with the platforms that are communicating with one another. As an example, consider that you are sending sensitive information over a network (for instance, your credit card number or bank password). A malicious user could obtain sensitive information from your transmission if they intercepted it. Generally speaking, encryption provides additional security for such transmissions by scrambling (encrypting) the data in a way that if it were intercepted, a third party would not be able to decode (unscramble) it. A recipient may, however, be able to decrypt the transmission.