Which layer provides node-to-node connectivity in the OSI model?

The Data Link layer is responsible for node-to-node connectivity in the OSI model. This layer facilitates the transfer of data between devices on the same local network and ensures that data is correctly packaged into frames for transmission. It is in charge of establishing, maintaining, and terminating the connection between two directly connected nodes, which is crucial for enabling reliable communication.

The significance of this layer includes error detection and handling, as well as managing access to the physical medium. It operates with MAC (Media Access Control) addresses, which are unique identifiers assigned to network interfaces for communications at this layer.

In contrast, the Physical layer deals with the actual transmission of raw bits over a physical medium, without any concern for how those bits are grouped or interpreted. The Network layer is focused on routing packets across multiple networks, while the Transport layer is responsible for end-to-end communication and ensuring complete data transfer, including error correction and flow control. Hence, while each of the layers serves a unique and essential function, it is the Data Link layer that specifically provides the crucial node-to-node connectivity.