The OSI Model.

THE OSI MODEL.

What is the OSI Model?

The main purpose of communicating with one computer is to share information. Suppose two computers are located in different places, and they want to exchange information on these two computers. Then when a computer sends data, the data will reach the destination through many media. When moving from source to destination, data should not be a problem, meaning there are some rules set out so that it can be reached quickly and freely. These rules are called protocols. The model that combines these protocols is called the OSI model. This model is called the OSI model.

The OSI model is divided into seven layers or layers.

Its levels are:

1. Applications.

2. Presentation.

3. Sessions.

4. Transport.

5. Networking.

6. Physical.

7. Data link.

 Application Layer:

This is the seventh layer of the OSI model. The application layer provides the user interface, and processes the network data. Applications that perform the application layer, resource sharing, remote file access, directory services, etc.

  

Presentation Layer:

This layer acts as a data translator for network services. The functions of this layer are data conversion, data compilation, decryption etc. The data formats used in this layer are JPG, MPG, etc.

Session Layer:

The function of the session layer is to connect the source and the destination device, control that connection and disconnect when needed. Three types of controls are used to transmit data.

Ø Simplex: Simplex's data flows more than once

Ø Half Duplex: In the Half Duplex method, data flow on one side ends when data flows on the other.

Ø Full Duplex: Full duplex method can simultaneously flow data.

Transport Layer:

The fourth layer of the OSI model is the transport layer. The function of this layer is to ensure that the data from the session layer is accessed reliably on another device. This layer uses two types of transmission to access the data:

 1. Connection oriented

Before sending data to the connection oriented, the sender creates a medium connection of a coinage signal with the customer. This happens in the case of TCT.

 2. Connectionless:

Before sending data to Connectionless Oriented, the sender does not make a connection with the customer through a carnage signal. This is the case with UDP.

Network Layer:

The function of the network layer is addressing and packet delivery. In this layer, by adding the network address to the data packet by encapsulation. The router is used in this layer and creates a routing table.

Data link layer:

This is the second layer of the OSI model. The function of the data link layer is to transmit the datagram from one device to another via a physical layer. This layer creates a logical link between the two devices. Converts the data into a frame in this layer.

Physical layer:

The bottom layer of the OSI model is the physical layer. This layer determines the way in which the signal will be transmitted from one device to another, what will be the electric signal or data bit format, etc. In this layer, data is transferred bit to bit. The devices used in this layer are hubs, switches, etc.

The signals are transferred in physical layer a cable, these bits are being converted to frame in the data link layer and as the frames pass through the router, the frames are being converted into packets. Now let's see how these pockets will go in connection oriented or in connectionless state. The session layer decides on which mode the segments will be transferred to after the transport layer has been decided. Then the presentation layer determines what format these data will be present in. Finally, the application layer created by the user interface.

  

Many times a question arises as to how many layers of application layer or network layer OSI model can easily remember this sentence.

 All people seem to need data processing

Ø P= Presentation layer

Ø A= Application layer

Ø S= Session layer

Ø T= Transport layer

Ø N= Network layer

Ø D= Data link layer

Ø P= Physical layer