Which layer of the OSI model covers physical cable connections?

The Physical layer (Layer 1) of the OSI model governs the electrical, optical, and mechanical specifications for transmitting raw bit streams over a network medium. It defines cable types, connector standards, voltage levels, and physical topology, making it the layer directly responsible for all physical cable connections. Every other OSI layer depends on Layer 1 to carry signals across the physical medium.

Layer 3 is the Network layer, responsible for logical IP addressing and routing decisions between networks, not physical cable connections.

Layer 5 is the Session layer, which manages the establishment, maintenance, and termination of communication sessions between application processes.

Layer 7 is the Application layer, which provides network services directly to end-user applications such as HTTP, FTP, and DNS.