OSI Model

Hamza Iqbal
2 min readDec 30, 2023

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OSI model: 7 layers

7- Application layer 6- Presentation layer 5- session layer 4- Transport layer 3- network layer 2- data-link layer 1- physical layer

Application layer: Software applications on web browsers are included in this layer, it required input from user to get data and that is the application layer. It includes http and smtp protocols. Software client desktop applications are not included in the application layer.

Presentation layer: Presentation layer is often called translation layer. It basically takes data from application layer and manipulate as per the requirement to transmit it over the network. The purpose of the presentation layer is translation, encryption/decryption and compression.

Session layer: Session layer establishes connection between two devices for the transfer of data. the time between the connection is opened and then is ended is called session. This layer ensures that the session is open long enough to transfer all the data and closes the session as soon as the transfer is complete to avoid wastage of resources.

Transport layer: It is responsible for end to end communication between the devices. It takes data from the session layer and breaks it down into chunks called segments before sending to the network layer. it also reassembles the segments on the receiving side so that the session layer can use that data.

Network layer: Network layer is responsible for transfer of data between different networks. It breaks down the segments received from the transport layer into smaller units called packets. It then reassembles all the packets on the receiving side. It also finds the best physical path for packets to move which is called routing. If both the devices are on same network then this layer is unnecessary.

Data-link layer: The data link layer facilities the data transfer between the two devices on the same network. The data link layer takes packet from the network layer and converts it into frames.

Physical layer: This layer includes the physical equipment involved in the transfer of the data. In this layer, the frames are converted to bits (string of 1, and 0)

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Hamza Iqbal
Hamza Iqbal

Written by Hamza Iqbal

Software engineer (MERN Stack)

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