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OSI Model Full Form in Computer Networking

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Introduction :

The OSI (Open Systems Interconnection) model is a conceptual framework that defines how computers communicate with each other over a network. It consists of seven layers, each with its own specific function and set of protocols.

Starting from the bottom, the first layer is the physical layer, which deals with the physical aspects of transmitting data such as cables, connectors, and signaling. The second layer is the data link layer, which is responsible for establishing and maintaining communication between two devices on the same network.

The third layer is the network layer, which handles the routing of data between networks. The fourth layer is the transport layer, which ensures reliable transmission of data between two devices.

The fifth layer is the session layer, which establishes and manages sessions between applications. The sixth layer is the presentation layer, which deals with the syntax and semantics of the data being transmitted.

Finally, the seventh layer is the application layer, which provides services to applications for network communication.

The OSI model is important because it helps network designers and administrators understand how different protocols and technologies work together to provide network communication. It also helps in troubleshooting network issues by isolating problems to specific layers.

OSI stands for Open Systems Interconnection. The OSI model was developed by the International Organization for Standardization(ISO). It is a reference model for how applications communicate over a network. The OSI model characterizes computing functions into a universal set of rules and requirements to support interoperability between different products and software. 


The OSI model can be considered a universal language for computer networking. It is based on the concept of divide and conquers, it splits up the communication system into 7 abstract layers, and the layer is stacked upon the previous layer. 

Layers of OSI Model

OSI model has seven layers which are as follows: 

  1. The Physical Layer
  2. The Data Link Layer
  3. The Network Layer
  4. The Transport Layer
  5. The Session Layer
  6. The Presentation Layer
  7. The Application Layer

Functions of OSI model:

Functions of OSI

To learn more about layers, visit Layers of OSI Model 


  • It is the conceptual model that enables the diverse communication systems to communicate using the network.
  • It was developed by the ISO (International Organization for Standardization) in 1984.
  • It acts as an architecture for inter-computer communications.
  • It is divided into 7 layers and each layer performs a particular task.
  • Each layer is independent of the other and can perform its operations independently.

Uses of the OSI model:

 Here are some of the key uses of the OSI model:

  1. Facilitates Communication: The OSI model defines a clear and standardized set of protocols for communication between different devices on a network. This ensures that devices from different manufacturers can communicate with each other seamlessly.
  2. Helps in Network Design: The OSI model helps network designers and administrators to understand how different protocols and technologies work together to provide network communication. This understanding is essential when designing new networks or upgrading existing ones.
  3. Simplifies Troubleshooting: If there is a problem in the network, the OSI model helps isolate the problem to a specific layer. This makes it easier for network administrators to troubleshoot and fix the issue quickly.
  4. Encourages Interoperability: The OSI model promotes interoperability between different devices and software from different vendors. This means that devices can work together regardless of their origin.
  5. Provides a Common Language: The OSI model provides a common language and framework for network communication. This helps network administrators and engineers to communicate effectively about network issues and solutions.

 key issues of the OSI model:

Here are some of the key issues of the OSI model:

  1. Too Complex: The OSI model has seven layers, which can make it difficult for some people to understand. This complexity can make it hard for network administrators to troubleshoot issues, as it can be challenging to determine which layer is causing the problem.
  2. Not Always Practical: The OSI model is a theoretical model that is not always practical in real-world network communication. In practice, some layers may be combined or omitted altogether.
  3. Not Widely Adopted: While the OSI model is widely used as a reference model, it is not always used in practice. Instead, many networks use a simplified model, such as the TCP/IP model.
  4. Limited Scope: The OSI model is focused solely on network communication and does not cover other aspects of computer systems, such as storage or processing.
  5. Limited Flexibility: The OSI model is a fixed model that does not allow for much flexibility in terms of adapting to new technologies or protocols.


  • It is a layered model and each layer is independent. Thus, changes in one layer don’t affect the other layers.
  • It divides the complex function into smaller parts.
  • It is a generic model as it has the flexibility to adapt to many protocols.
  • It supports both connection-oriented as well as connectionless services.
  • It is more secure and adaptable than having all services bundled in a single layer.


  • It is purely a theoretical model and ignores the availability of resources and technologies. Hence, its practical implementation is somewhat restricted.
  • It is very complex. The initial implementation was cumbersome, slow, and costly.
  • The layers are interdependent, they can’t operate parallelly as they have to wait for the data/ packets from the predecessor layer.

Last Updated : 16 Apr, 2023
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