The application layer is the OSI layer that is closest to the end user; this means that both the OSI application layer and the user interact directly with the software application.
This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication.
When identifying communication partners, the application layer determines the identity and availability of communication partners for an application that has data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, the application layer manages all communication between applications. Some examples of application layer implementations include TCP/IP applications and OSI applications. TCP/IP applications are protocols, such as Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP) that exist in the TCP/IP protocol suite. OSI applications are protocols, such as File Transfer, Access, and Management (FTAM), Virtual Terminal Protocol (VTP), and Common Management Information Protocol (CMIP) that exist in the OSI protocol suite.
Was this article helpful?