In data network terminology, what is a frame?

In data network terminology, a frame is defined as a unit of data at the link layer of the OSI model. The link layer is responsible for node-to-node data transfer and handles the physical addressing and error detection, ensuring that data is transmitted correctly over the physical medium. A frame encapsulates the packets from the network layer and adds necessary information such as source and destination MAC addresses, control information, and frame check sequences for error checking.

In contrast, the other layers mentioned in the options serve different purposes: the application layer manages user interface and application-level messages, the transport layer provides end-to-end communication and error recovery, and the internet layer, associated with routing and logical addressing, deals with packet forwarding. Thus, framing is exclusively a function of the link layer, distinguishing it clearly from the functions of other layers in the OSI model.