Session, Presentation, and Application Layers - OSI Reference Model

Session, Presentation, and Application Layers

Let’s look at the upper layers of the OSI seven layer model now. Those layers are the transport, session, presentation, and application layers.

Session Layer

  - Network File System (NFS)
  - Structured Query Language (SQL)
  - Remote-Procedure Call (RPC)
  - X Window System
  - AppleTalk Session Protocol (ASP)
  - DEC Session Control Protocol (SCP)
The session layer establishes, manages, and terminates sessions among applications. This layer is primarily concerned with coordinating applications as they interact on different hosts. Some popular session layer protocols are listed here, Network File Systems (NFS), Structured Query Language or SQL, X Window Systems; even AppleTalk Session Protocol is part of the session layer.

Presentation Layer

The presentation layer is primarily concerned with the format of the data. Data and text can be formatted as ASCII files, as EBCDIC files or can even be Encrypted. Sound may become a Midi file. Video files can be formatted as MPEG video files or QuickTime files. Graphics and visual images can be formatted as PICT, TIFF, JPEG, or even GIF files. So that is really what happens at the presentation layer.

Application Layer

The application layer is the highest level of the seven layer model. Computer applications that you use on your desktop everyday, applications like word processing, presentation graphics, spreadsheets files, and database management, all sit above the application layer. Network applications and internetwork applications allow you, as the user, to move computer application files through the network and through the internetwork.

Examples:-

COMPUTER APPLICATIONS

  - Word Processor
  - Presentation Graphics
  - Spreadsheet
  - Database
  - Design/Manufacturing
  - Project Planning
  - Others

NETWORK APPLICATIONS

  - Electronic Mail
  - File Transfer
  - Remote Access
  - Client-Server Process
  - Information Location
  - Network Management
  - Others

INTERNETWORK APPLICATIONS

  - Electronic Data Interchange
  - World Wide Web
  - E-Mail Gateways
  - Special-Interest Bulletin Boards
  - Financial Transaction Services
  - Internet Navigation Utilities
  - Conferencing (Voice, Video, Data)
  - Others