What is the PDU of the Session Layer?

• A. segments
• B. bits
• C. data
• D. frames

Answer: (C)

In this layering view, PDUs are labeled differently as information moves through the stack. The upper layers—Application, Presentation, and Session—handle data from the user or higher layers, and they don’t introduce a new, widely used PDU name like segments or frames. The Session Layer focuses on establishing, maintaining, and terminating dialogs, not on creating a distinct unit of transmission. Therefore, the PDU at this layer is simply data. The transport layer is the one that uses segments as its PDU, the data link layer uses frames, and the physical layer uses bits.