Which OSI layer is primarily responsible for defining hardware connections?

The Physical Layer is primarily responsible for defining hardware connections within the OSI model. This layer deals with the physical medium of data transmission, which includes specifications for electrical signals, optical signals, and radio frequency signals used for data communication. It defines the characteristics of the hardware components, such as cables, switches, and network interface cards, as well as the methods for transmitting raw bits over a physical connection.

This layer plays a crucial role in ensuring that devices can communicate effectively at the hardware level. By specifying how data is transmitted through various physical media, the Physical Layer enables different devices and technologies to interoperate within the network.

In contrast, the other layers focus on different aspects of network communication. The Data Link Layer is concerned with framing and error detection, the Network Layer manages addressing and routing of data packets, and the Transport Layer is responsible for end-to-end communication and flow control. Therefore, while they are essential for efficient networking, they do not define the hardware connections themselves.