The Network Layer is to packet as the Data Link Layer is to:

The correct answer is that at the Data Link Layer, the unit of data is referred to as a frame. This layer is responsible for node-to-node data transfer and is tasked with framing the packets received from the Network Layer into frames suitable for transmission over the physical medium.

Frames include not only the payload data but also the necessary control information such as source and destination MAC addresses, error detection codes, and sometimes other protocol-specific headers. By encapsulating packets into frames, the Data Link Layer ensures that the data can be correctly delivered to the intended recipient on the same local network segment.

Understanding this structure is essential for grasping how data is transferred across different layers of the OSI (Open Systems Interconnection) model, where each layer serves a specific function and operates with its own data unit terminology.