What is the PDU of the Network Layer?

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

Answer: (D)

The PDU at the Network Layer is a packet. This layer is responsible for routing and logical addressing, so it takes the data handed down from the Transport Layer (a segment) and adds its own header with IP addresses, TTL, routing information, and other network-layer fields. The result—the header plus the encapsulated segment—is the packet that moves through routers toward its destination. In contrast, the Data Link Layer works with frames, the Transport Layer with segments, and the upper layers with data or messages. So identifying the Network Layer’s PDU as a packet aligns with its role in routing and addressing across the network.