Answer:
The IP datagram is constructed at the Network Layer, which is Layer 3 in the OSI model.
Step-by-step explanation:
The IP (Internet Protocol) datagram is constructed at the Network Layer, also known as Layer 3, in the OSI (Open Systems Interconnection) model. The Network Layer is responsible for addressing, routing, and fragmentation/reassembly of data packets. It encapsulates the upper-layer data into an IP datagram by adding a header that contains the necessary information for routing and delivering the packet across networks. The IP datagram includes the source and destination IP addresses, protocol information, and other control fields required for proper transmission and handling of the packet by network devices.