Which OSI layer is responsible for data payload being added to a PDU during encapsulation?

• A. Data Link Layer
• B. Network Layer
• C. Application Layer
• D. Transport Layer

Answer: (C)

Encapsulation is layering headers as data moves down the stack, and the actual user data is created at the Application Layer. That data becomes the payload that the next layer wraps with its own header to form a segment at the Transport Layer. The Transport Layer’s header turns that into a segment whose payload is the Application data; then the Network Layer adds an IP header to create a packet, and the Data Link Layer adds its frame header and trailer to form a frame, all carrying the same underlying data payload. So the data that ultimately becomes the payload inside each PDU originates at the Application Layer.