What level of the International Organization for Standardization's reference model is responsible for the actual transmission of data and handshaking signals?

The physical layer of the International Organization for Standardization's reference model is responsible for the actual transmission of data and handshaking signals. This layer deals with the physical aspects of communication, including the hardware elements involved in sending and receiving data over a network. It defines the electrical and physical specifications for devices, such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors.

At this level, the focus is on the raw bit transmission over various media, such as copper cables, fiber optics, or radio waves. Handshaking signals, which are essential for establishing and controlling a data connection, are also managed at the physical layer, ensuring that devices can communicate with each other effectively and reliably.

Other layers, such as the application layer and the transport layer, handle higher-level functions like data formatting and error checking, while the session layer facilitates the establishment, maintenance, and termination of connections but does not engage in the physical delivery of the signals themselves.