OSI Upper Layers

The upper layers of the OSI model just store collections of functions used commonly to interface between software applications and the Transport layer.

The Session layer (Layer 5) is responsible for exchanging messages between a client and a server, and this stream of messages is called the session.

The Presentation layer (Layer 6) transforms between Session layer data and the Application's data format. A common example of this is translating between ASCII and Unicode.

The Application layer (Layer 7) is at the top of the OSI stack. It doesn't wrap any protocols or functions for those protocols. They're responsible for interfacing between the end user and the Transport layer.

The upper layers of the OSI model are just responsible for making a computer network useful rather than functional. Web browsing,