Which OSI layer is responsible for connection establishment, session maintenance, and authentication?

Which OSI layer is responsible for connection establishment, session maintenance, and authentication?

• A. Layer 2 Data Link
• B. Layer 5 Session
• C. Layer 3 Network
• D. Layer 1 Physical

Answer: (B)

The main idea is that the session layer coordinates conversations between two endpoints. It establishes the connection, keeps the interaction alive as long as the session lasts, handles dialog control (who talks when), and terminates the session when done. It can also incorporate authentication as part of starting a session, ensuring both sides are trusted before communication continues, and it provides mechanisms to recover or resume a session if something goes wrong. The data link layer is about delivering frames on a local link, the network layer is about routing across networks, and the physical layer handles the actual signals over the medium; none of these manage the ongoing state of a multi-step dialogue the way the session layer does.

The main idea is that the session layer coordinates conversations between two endpoints. It establishes the connection, keeps the interaction alive as long as the session lasts, handles dialog control (who talks when), and terminates the session when done. It can also incorporate authentication as part of starting a session, ensuring both sides are trusted before communication continues, and it provides mechanisms to recover or resume a session if something goes wrong. The data link layer is about delivering frames on a local link, the network layer is about routing across networks, and the physical layer handles the actual signals over the medium; none of these manage the ongoing state of a multi-step dialogue the way the session layer does.