What is OSI Layer 5?

Understanding OSI Layer 5

Session layer. Layer 5 of the OSI model manages sessions or connections between applications on different devices. It establishes maintains and terminates dialogues between devices handles session checkpointing and recovery and controls synchronization between endpoints. Session layer protocols include NetBIOS and RPC. Security at this layer addresses session hijacking and man-in-the-middle attacks. Session layer security is addressed in standards like NIST SP 800-53 ISO 27001 and application security frameworks. Organizations implement Layer 5 security through session management controls secure session establishment authentication token validation and timeout mechanisms. For example a web application might implement robust session management including secure session tokens session timeouts after periods of inactivity session regeneration after privilege changes and validation measures to prevent session hijacking or fixation attacks. Related terms Session management Dialog control Session token Session hijacking NetBIOS RPC Checkpointing Session fixation.