Which OSI layer is responsible for establishing, managing, and terminating connections between applications across a network?

• A. Physical Layer (Layer 1)
• B. Session Layer (Layer 5)
• C. Data Link Layer (Layer 2)
• D. Transport Layer (Layer 4)

Answer: (B)

The question tests how conversations between applications are coordinated across a network. This is handled by the session layer, which establishes, maintains, and terminates sessions between application processes. It also provides dialog control—deciding who talks when—and adds synchronization points for long communications so operations can be resumed safely if needed. This layer effectively manages the logical connection state between applications, separate from how data is physically transmitted or how the data is delivered end-to-end.

Why not the others: the physical layer deals with raw signaling and the electrical/physical medium, not connections between applications. The data link layer handles framing and node-to-node transfer on a single link, with error detection and access control. The transport layer provides end-to-end delivery, reliability, and flow control, but it doesn’t manage the ongoing session state or dialogue control between two application processes, which is the session layer’s role.