OSI MODEL
Presentation layer prepares the
data. It takes data from application layer and mark it with formatting code
such as .doc, .jpg, .txt, .avi etc. These file extensions make it easy to
realize that particular file is formatted with particular type of application.
With formatting presentation layer also deals with compress and encapsulation.
It compress or decompress the data file. This layer can also encapsulate the
data, but it’s uncommon as this can be handle by lower layers more effectively.
Session layer deals with
connections. It establishes, manages, and terminates sessions between two
communicating node. This layer provides its services to the presentation layer.
Session layer also synchronizes dialogue between the presentation layers of the
two hosts and manages their data exchange. For example, web servers may have
many users communicating with server at a given time. Therefore, keeping track
of which user communicates on which path is important and session layer handle
this responsibility accurately.
Transport Layer
- It sets up and maintain the connection between two devices.
- It multiplexes connections that allow multiple applications to simultaneously send and receive data.
- According to requirement data transmit method can be connection oriented or connection less.
- For unreliable data delivery connection less method is used.
- Connection less methods use UDP protocol.
- For reliable data delivery connection oriented method is used.
- Connection oriented methods use TCP protocol.
- When Implemented a reliable connection, sequence numbers and acknowledgments (ACKs) are used.
- Reliable connection controls flow through the use of windowing or acknowledgements.
- Segmentation
- Connection management
- Reliable and unreliable data delivery
- Flow control
- Connection multiplexing
