The protocol data unit (PDU) for the application layer in the Internet stack is
(A) Segment
(B) Datagram
(C) Message
(D) Frame
Answer: (C)
Explanation: The Protocol Data Unit is the unit of communication at a particular layer.
The Layer 1 (Physical Layer) PDU is the bit or, more generally, symbol
The Layer 2 (Data Link Layer) PDU is the frame.
The Layer 3 (Network Layer) PDU is the packet.
The Layer 4 (Transport Layer) PDU is the segment
for TCP or the datagram for UDP.
The Layer 5 (Application Layer) PDU is the data or message.