Application Layer 's Function

In the Open Systems Interconnection (OSI) communications model, the application layer provides services for an application program to ensure that effective communication with another application program in a network is possible. The application layer is not the application itself that is doing the communication. It is a service layer that provides these services:

* Makes sure that the other party is identified and can be reached
* If appropriate, authenticates either the message sender or receiver or both
* Makes sure that necessary communication resources exist
* Ensures agreement at both ends about error recovery procedures, data integrity, and privacy
* Determines protocol and data syntax rules at the application level

It may be convenient to think of the application layer as the high-level set-up services for the application program or an interactive user.