Importance of The Physical Layer in the OSI Reference Model

Welcome to my OSI Reference Model study class. Today, I will explain the first layer and its functions in a network. I will also explain the devices working in the first layer of the OSI Reference Model.

The physical layer is the first layer in the OSI model that deals with the physical transmission medium. The data transferred via the physical layer is in the form of electrical signals.

In real life, we can treat the physical layer as the road where the vehicles are passing. There is a reason why I chose the road to explain the Physical Layer. The road is the one which is carrying the vehicles and linking the cities.

Like that example, the physical layer transmits the data signal in electrical signals and connecting nodes.

We can consider the road as the physical layer and vehicles as the electric signals. Just replace the city with a node. I guess you understand the concept.

The physical layer is all about the connections. So, which cables do we use in this layer to form a network?

We use the following three types of cables to form a computer network. They create the physical layer of a network.

1. Coaxial cable

2. Twisted pair cable

3. Optical fiber cable

Tito Mathew asked about the devices that work in this layer. I recommend everyone to learn it. Sometimes, interviewers may ask about the devices working in the physical layer. They are:

1. Internet gateway

2. Hub

3. Repeater

James Anderson asked me about the functions of the OSI Reference Model's first layer. The functions and responsibilities of the physical layer are:

1. Bit-by-bit delivery

2. Modulation

3. Encoding and Signaling:

4. Bit synchronization

5. Physical Network Topology

In the Physical Layer, data flows in the form of an electric pulse, and the cables are responsible for the safe delivery of the signals. The physical layer is responsible for varying the waveform for the data transfer. This process is known as modulation.

The physical layer is also responsible for various types of encoding and decoding of signals.

The physical layer cares about the transmission mode. It is also the physical layout of the network( topology).

The seven layer structure of the OSI Reference Model is:

1. Physical layer
   
   
2. Data link layer
   
   
3. Network layer
   
   
4. Transport layer
   
   
5. Session layer
   
   
6. Presentation layer
   
   
7. Application layer