OSI model revisited
Session Layer initiates, maintains, and terminates each logical session between end users = sessions (cf., telephone conversations); controlled abortions
Presentation Layer formats the data for presentation to the user; accommodates different interfaces on different terminals, computers and application programs
(displaying, formatting, editing user input and output)
Application Layer is the end user access to the network: provides a set of utilities for application programs; network management statistics, remote system initiation, termination, network monitoring, application diagnostics, transparency, processor sharing, use of distributed data bases, and industry specific protocols (e.g., banking)