What is Physical Layer ? | Layer -1

Ø  Physical layer deals with physical transmission of binary data on a given media(Copper, Fiber, Wireless….etc)

Ø  Devices work at physical layer are Hub, Modems, Repeaters and transmission media

The physical layer is also concerned with the following:

1. Physical characteristics of interfaces and medium:

•     The physical layer defines the characteristics of the interface between the devices and the transmission medium.

•     It also defines the type of transmission medium

2. Representation  of  bits:

•     The physical   layer data   consists   of a   stream  of bits (sequence  of Os  or  1s)  with no  interpretation. 

•     To  be  transmitted,  bits  must be encoded into signals electrical or optical. The physical layer defines the type of encoding (how Os and Is are changed to signals).

3. Data rate/ Transmission rate:

•     The number of bits sent each second-is also defined by the physical layer.

•     In other words, the physical layer defines the duration of a bit, which is how long it lasts.

4. Line configuration:

•     The physical layer is concerned with the connection of devices to the media.

•     In a point-to-point configuration, two devices are connected through a dedicated link.

•     In a multipoint configuration, a link is shared among several devices.

5. Physical topology:

•     The physical topology defines how devices are connected to make a network.

6. Transmission mode:

•     The physical layer also defines the direction of transmission between two devices: simplex, half-duplex, or full-duplex.