defines the hardware, cabling wiring, power output, pulse rate, etc. (osi layer)
• synchronizing bits • how bits are represented on the medium • wiring standards for connectors and jacks • physical topology • bandwidth usage • multiplexing strategy
defines the physical characteristics of the transmission medium (connectors, pins, electrical currents, encoding, light modulation, etc) rj-45, ethernet (ieee 802.3) lan hub, lan repeater, cables