Layer 7. The Application Layer

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This highest layer in the OSI architecture ultimately leads the outside world —the end-user. However, the Application Layer is not itself the user application; it only provides the system independent interface to the actual data communications application and its own user interface (though applications may indeed perform Application Layer functions).

Although the highest and seemingly the most abstract layer, the Application Layer actually consists of a complex set of standards and protocols. Application Layer Protocols are classified into Common Application Specific Elements (CASE) and Specific Application Specific Elements (SASE).

Layer 7 is where communication partners are identified, quality of service is identified, and user authentication and privacy are determined. This layer contains functions for applications services, such as file transfer, database processing, e-mail, remote file access and virtual terminals.

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