What layer in the OSI model is responsible for defining hardware addresses?

The Data Link layer in the OSI model is responsible for defining hardware addresses. This layer is crucial because it provides the means for transferring data between devices on the same local network. It facilitates the physical addressing of devices through hardware addresses, commonly known as MAC (Media Access Control) addresses. Each device on a network interface is assigned a unique MAC address, allowing it to be identified and communicated with on a local network segment.

In addition to hardware addressing, the Data Link layer handles error detection and correction, framing, and manages how data is packaged for transmission. This ensures that data packets are delivered reliably to the correct hardware address, establishing a direct connection between networked devices.

The other layers have different responsibilities; for instance, the Transport layer focuses on end-to-end communication and reliability, the Network layer handles routing and logical addressing, and the Application layer interfaces directly with end-user applications. Hence, while each layer plays an important role in networking, it is the Data Link layer that specifically deals with hardware addresses.