What is physical layer of OSI model?

What is physical layer of OSI model?


Definition of Physical layer

Working of physical layer

Disadvantages of  this layer

Physical layer of OSI model:

This layer is the first layer of the OSI/ISO model.In this layer data in bits form send from one computer to another computer.This layer is not concern with the meanings of bits. It deals with the setup of physical connection to the networks.It transmit the signals.This layer is the lowest layer of the OSI/ISO model.

Physical layer of OSI model


Working of Physical Layer:

Representation of Bits:
In this layer data consists of bits.These bits are encoded into signals for the transmission.
It encode the data 0’s and 1’s into signal.
Data Rate:
It also defines the rate of transmission.Which consists of the number of bits per second.
This layer deals with the synchronization of the transmitter and receiver too.Sender and receiver are synchronize at bit level.
This layer define the transmission interface between transmission medium and devices.
Line Configuration:
Physical layer connects devices with Point to Point configuration.It also connect devices with Multi-point configuration.
All devices are connects with other devices by topology such as,Bus,Star, Mesh and Ring.
Transmission Modes:
It also tell about transmission mode of two devices such as Simplex, Half Duplex and Full Duplex.




Problem in this Layer:

As this layer is concern with transmitting raw bits.The design issue creates when data is ! bit and receive as 0 bit.
Some question are here:

  • How many volts are use to represent a 1 bit and 0 bit?
  • How many nanoseconds (ns) a bit lasts?
  • This (physical) layer is the lowest layer of the OSI Model.
  • This layer activates,deactivates and maintains the physical connection.
  • This is responsible for transmission and reception.
  • All detail of voltages and data rates is define in the physical layer.
  • Conversion of digital/analog bits into electrical signal or optical signals take place in this layer.
  • Encoding of data is also done in physical layer.

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