The application layer provides the services required for an application program running on one system to interact with an application program running on another system. The functions performed at this layer include establishing contact between the two processes, setting conditions of the interaction, providing means to execute a command on the other system, accessing each other's file systems, insuring reliable exchange of information, and other functions directly used by an application program. Only those parts of an application that are involved in communication with another system are part of the application layer. Those parts of the application process are called the application entity.  Examples are kermit, ftp, appleshare file server, telnet, and NFS mounts.