Which OSI layer is known for handling the raw transmission of bits over a physical medium?

The Physical Layer is responsible for managing the raw transmission of bits over a physical medium in the OSI model. This layer deals with the hardware elements of networking, including the electrical signals, optical signals, and the physical medium itself, such as cables or fiber optics. It establishes and terminates the connection to the physical medium, ensuring that data can be transmitted and received as binary data (1s and 0s).

This layer also defines characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and the physical connectors used. Essentially, without the Physical Layer, the higher layers of the OSI model, which handle data formatting, error correction, and ultimately the user interactions, would have no means of transmitting that data over a network.

In contrast, the other OSI layers each serve distinct functions that build upon the foundation established by the Physical Layer. The Data Link Layer, for instance, is responsible for node-to-node data transfer and error detection/correction, while the Network Layer handles the routing of packets through logical addressing across multiple networks. The Application Layer provides the interface for end-user applications to communicate over the network, isolating them from the complex operations of the underlying layers.