Application Layer

The application layer provides functions for the applications. This layer connects to the lower layers. At this level, data entry and output also takes place. As a service to application programs, this layer ensures that efficient communication with other application programs within a network is possible. The application layer itself is not the application that performs the communication. Rather, it represents a service layer that provides the following services:

• Make sure that the other party is identified and can be reached.
• If necessary: ​​authenticate the sender of the message, the recipient or both.
• Make sure that the necessary conditions for communication exist (for example: Is there a modem in the sender's computer?).
• Agree on both sides of troubleshooting, data integrity, and privacy procedures.
• Set the application-level protocol and data syntax rules.

One can easily think of the application layer as a highly efficient setup service for an application or an interactive user.