What Is the OSI Model? Explain 7 Layer of OSI Model with uses and Advantages

OSI model or Open Systems Interconnection Model is an intellectual framework. It demonstrates seven layers that are used by a computer system to communicate over a network. Moreover, it is created by the International Organization for Standardization (ISO) to regulate digital communication via standard protocols. 

Key points of the OSI Model are:

  • It has seven layers to perform a specific function.
  • It was created by ISO in 1984 to explore inter-computer communications.
  • The model is mainly divided into two layers: upper and lower layers
  • Upper Layers: It deals with issues related to application and is implemented only in software.
  • Lower Layers: These layers deal with concerns associated with data transportation.
  • In the OSI model, encapsulation or decapsulation is required to move data between layers.

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Layers of OSI Model

1.Physical Layer

The very first layer of the OSI model is the physical layer. It deals with the physical movement of data between computers. The prominent layer is to transmit a bit from one to another node. Moreover, it acts as the lowest layer of the model.


  • It helps to establish, deactivate, and maintain the physical connection.
  • The physical layer is responsible for line configuration, data transmission, signals, and topology.
  • It explains the data encoding onto the media for smooth data transmission such as a hub.


  • It allows physical devices (fiber optic cable, radio frequencies, and copper writing) to transmit data.

2.Data-Link Layer

It is an important layer of the OSI model responsible for error-free transportation of data frames.  It describes data format on the network and provides effective communication between two or more devices. Furthermore, the data-link layer allows users to identify each device residing on the local network. It includes two sublayers: the logical link control layer and the media access control layer.


  • It is responsible for the movement of frames from one to another node.
  • It describes the protocols: Ethernet Protocol and Point-to-Point Protocol (PPP).
  • If any error occurs in physical error, the data-link layer can rectify it.
  • The predominant functions of the layer are framing, physical addressing, flow control, error control, and access control.
  • The device examples of the data-link layer of the model are switches and bridges.

3.Network Layer

Do you know about end-to-end communications? The third layer of the OSI is the network layer, which manages end-to-end communication. It seeks the best path to transfer data from its source to its destination. Also, it is responsible for routing and forwarding the packets (data). It works under the Network layer protocol such as IP and Ipv6.


  • The network layers allow internetworking, addressing, packetizing, and routing.
  • Through routing, the layer finds the best path for data to reach its destination.


  • The best example of the network layer is the router.

4.Transport Layer

As the name indicates, the transport layer helps in data transportation that includes TCP and UDP. It takes the data from the higher layer of the OSI model and breaks it into different segments. So that, it can send to lower layers of the model. On the contrary, the layer also reassembles the segments into data to make it usable by the higher-level protocols and applications.


  • The transport layer makes sure the reliability of sent data.
  • The functions of the layer include service-point addressing, connection control, flow control, and error control. Importantly, it also manages the segmentation and reassembly of data.
  • It puts segments in the right order which is called sequencing.
  • It is also called the heart of the OSI Model.
  • The transport layer offers connection-oriented and connectionless services.
  • It also manages the end-to-end delivery of the complete message.


  • The message can be successfully delivered by the transport layer. 

5.Session Layer

The session layer is an important layer of the model and is responsible for communication. Here, the session is defined as the time when the communication is open and closed. The layer makes sure the session stays open enough to perform the complete data exchange. It also ensures the session must close at the right time to avoid time wastage. Moreover, it establishes, manages, and terminates the connections. With the layer, it gets easy to establish duplex, half-duplex, or simplex communication among devices.


  • The layer develops the procedures for establishing, restarting, termination, or recovery.
  • It tackles dialog control and synchronization.
  • The session layer ensures security.

6.Presentation Layer

The presentation layer or translation layer manages the presentation of the data on the network. It tackles the three predominant tasks, including translation, compression, and encryption. It has concerns with the syntax and semantics of the information transformed from one to another system.


  • The presentation layer acts as a data translator for a network.
  • It is the part of the operating system converting the data between the formats.
  • It also compresses the data before sending it to the next layer. Consequently, it improves the speed and efficiency of communication.
  • With the layer, encryption and decryption can be handled that is required by the application layer.


  • It prepares the data so that the application layer can use it successfully.

7.Application Layer

The application layer helps to interact with data from the user. It allows application software or operating systems to communicate on the network by providing all required services or protocols. For example, HTTP is used by the Firefox web browser and POP3 may be used by e-mail programs.


  • It manages the concerns related to network transparency, resource allocation, and more.
  • It offers network services to the end-users.
  • The primary functions of the layer are file transfer, access, and management (FTAM) and mail services.


  • It allows software applications and email clients to begin communications.
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