Layer 6 of the seven-layer Open Systems Interconnection (OSI) reference model. The presentation layer structures data that is passed down from the application layer into a format suitable for network transmission. This layer is responsible for data encryption, data compression, character set conversion, interpretation of graphics commands, and so on. The network redirector also functions at this layer.
Presentation layer (OSI Model)
This layer is not always used in network communications because it's functions are not always necessary. Translation is only needed if different types of machines need to talk with each other. Encryption is optional in communication. If the information is public there is no need to encrypt and decrypt info. Compression is also optional. If files are small there is no need for compression.
Most real-world protocol suites, such as TCP/IP, do not use separate presentation layer protocols. The presentation layer is mostly an abstraction in real-world networking.