Layer 1: Physical layer:-

       The 1^st layer of OSI model is the physical layer. The function of this layer is the transmission of bits over the network media i.e. it provides a physical connection for the transmission of data among the network devices.

                    IT is responsible for following:-

v It defines the electrical and physical specifications of the data connection. It defines the relationship between a device and a physical transmission medium (e.g., a copper or fiber optical cable). This includes the layout of pins, voltages, line impedance, cable specifications, signal timing, hubs, repeaters, network adapters, host bus adapters (HBA used in storage area networks) and more.

v  It defines the protocol to establish and terminate a connection between two directly connected nodes over a communications medium.

v  It may define the protocol for flow control.

v  It defines a protocol for the provision of a (not necessarily reliable) connection between two directly connected nodes, and the modulation or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over the physical communications channel. This channel can involve physical cabling (such as copper and optical fiber) or a wireless radio link.