In ISO-OSI architecture, there are seven layers in this model. Starting from physical layer (layer 1), then data link layer, network layer, transport layer, session layer, presentation layer, application layer (layer - 7) respectively.Session layer:Session layer is the network dialog controller. It establishes, maintains and synchronizes the interaction among communicating system. It is responsible for dialog control, token management and synchronization in the network.Dialog control: Session layer allows two systems to enter into a dialog. It allows the communication between two processes to take place in either half-duplex or full “ duplex.Synchronization: It allows a process to add checkpoints to a stream of data.Token management: It prevents two parties from attempting the same critical operation at the same time.