Which OSI layer is responsible for establishing, managing, and terminating connections?

The session layer is crucial for establishing, managing, and terminating connections between applications on different devices. Its primary role is to create and maintain the session – this can involve setting up the connection, controlling the dialogue about how data is exchanged, and ensuring that the session can be gracefully terminated once communication has finished. This layer provides services such as dialog control, synchronization, and checkpointing, which help in managing ongoing interactions effectively.

In contrast, while the transport layer focuses on delivering data segments reliably and ensuring error recovery and flow control, the session layer takes on the responsibility of managing the session state. The network layer is primarily involved with routing data packets and addressing, ensuring that data can travel effectively from one device to another through various networks, without dealing directly with the management of connections. The application layer is the closest layer to the end user, dealing with application-specific functionalities and user interface, rather than connection management. Thus, the session layer is the appropriate answer for the role of managing and controlling connections.