What is OSI Layer 1?

Understanding OSI Layer 1

Physical layer. Layer 1 of the OSI model defines the electrical mechanical procedural and functional specifications for activating maintaining and deactivating physical connections. It specifies characteristics like voltage levels timing physical data rates and physical connectors. Security at this layer involves protecting physical transmission media and interfaces. Physical layer security is addressed in standards like ISO 27001 NIST SP 800-53 and various industry-specific guidelines. Organizations implement physical layer security through cable protection electromagnetic shielding physical access controls tamper-evident seals and monitoring. For example a financial data center might secure physical layer connections by routing networking cables through protected conduits implementing electronic surveillance of wiring closets using tamper-evident seals on network jacks and regularly inspecting for unauthorized taps or devices. Related terms Physical security Electromagnetic interference Cable protection Signal jamming Wiretapping Hardware security Transmission media.