Layer 7, the highest layer, of the Open Systems Interconnection (OSI) Reference Model. Software at the Application Layer provides support services for user and application tasks such as file transfer, interpretation of graphic formats and documents, document processing, and user authentication in remote access applications. X.400 e-mail messaging, for example, takes place at Layer 7. TCP/IP application protocols such as Simple Mail Transfer Protocol (SMTP), Telnet, and File Transfer Protocol (FTP) also take place at this layer. See also e-mail, FTP, layer, network architecture, OSI Reference Model, SMTP, Telnet, and X.400.