Session Layer

This is fifty layer of OSI model. This layer establishes, manages, synchronizes and terminates connection between the computers. It also sets up, coordinates and terminates interactions and dialog between communicating devices. It provides either half duplex or fill duplex service.

This layer receives data from the presentation layer. It adds header and synchronization bits to the data and passes data to the transport layer. At the receiver side. session layer receives data from transport layer. It detaches header and synchronization bits from the data and passes data to the presentation layer.


  • Dialog Control :- This session layer is responsible for setting up session between communicating devices. It allows two devices to enter into dialog. These dialog can take place either in half-duplex or fill duplex mode dialog control is implemented using a data token. The user that has the token is only allowed to send the data. When the user is done with the operation the token is passed on to next user.
  • Synchronization :- At the session layer, checkpoint  are added into stream of data synchronization the session.