What is the primary purpose of a Physical Layer protocol?

The primary purpose of a Physical Layer protocol is to transmit bits across a physical medium. This layer is fundamental in the OSI (Open Systems Interconnection) model, as it deals with the actual hardware transmission of raw data over physical connections, such as cables or wireless channels. It defines the electrical, mechanical, and procedural specifications needed to facilitate the transmission and reception of unstructured raw bits over a physical medium. This includes aspects such as voltage levels, timing of voltage changes, and physical connectors.

While encryption, routing, and flow management are essential components of network communication, they occur at higher layers of the OSI model, such as the transport or network layers. For instance, encryption for secure transmission would typically involve protocols that operate above the Physical Layer, just as flow management and routing functionalities pertain to ensuring the efficiency of data transmission rather than the physical act of sending bits. Therefore, the focus of the Physical Layer is exclusively on the transmission of raw bits rather than any logical or secure processing of the data.