Networking - Network Models - OSI - Session Layer

The Session Layer is the fifth layer in the OSI model, residing above the Transport Layer. It is responsible for establishing, maintaining, and terminating sessions or connections between applications running on different hosts.

Key Features:

  • Session Establishment: The Session Layer handles the establishment of sessions between communicating applications. It establishes and manages the communication sessions required for data exchange.
  • Session Maintenance: Once a session is established, the Session Layer ensures its continuous operation. It manages the session duration, monitors the session for any interruptions, and handles session recovery if necessary.
  • Session Termination: The Session Layer is responsible for gracefully terminating the established sessions between applications.

Main Responsibilities:

  • Session Management: The Session Layer manages the communication sessions between applications. It handles session establishment, authentication, authorization, and synchronization between communicating hosts.
  • Dialog Control: The Session Layer controls the dialog between applications during a session. It establishes rules for initiating and terminating conversations, as well as managing turn-taking between applications.
  • Session Recovery: If a session is interrupted or terminated unexpectedly, the Session Layer is responsible for recovering and resuming the session, ensuring data integrity and consistency.


While the Session Layer is not implemented as a separate layer in most modern network protocols, session management tasks are often handled by the application layer or integrated within the transport layer protocols.