This tutorial explains the advantages, disadvantages, and basic purposes of the OSI model in detail. Learn why the OSI Model was created along with the purposes and benefits of the OSI model.
A networking model describes how information is transferred from one networking component to another. Just like a house blueprint defines the materials and technologies that are used in constructing the house, a networking model defines the protocols and devices that are required in building the network.
Technically, a networking model is a comprehensive set of documents that describes how everything should happen in the network. Individually, each document describes a functionality, protocol, or device that is required by a small portion of the network.
Why was the OSI Model created?
In starting days of computer networking, vendors created proprietary networking models to support their products. The biggest problem with these models was that they allowed communication only between the devices that were manufactured by the same vendor. For example, a computer manufactured by IBM was able to communicate only with the computer or networking device that was also manufactured by IBM.
This situation was neither good nor profitable for both manufacturers and consumers. It not only forced manufacturers to make all essential networking devices but also forced consumers to buy all devices from the same manufacturer.
To break this barrier, leading hardware manufactures agreed to use or support a vendor-neutral networking model along with their proprietary networking model. To create a vendor-neutral networking model, two major efforts were made.
The first one was made by ISO, and the second one was made by DoD. ISO (The International Organization for Standardization) created the OSI (Open Systems Interconnection) model and DoD (U.S. Department of Defense) created the TCP/IP model.
This tutorial is the first part of the article "Networking reference models explained in detail with examples". Other parts of this article are the following.
OSI Seven Layers Model Explained with ExamplesThis tutorial is the second part of the article. It explains the seven layers of the OSI model in detail.
Similarities and Differences between OSI and TCP/IP ModelThis tutorial is the third part of the article. It compares the OSI reference model with the TCP/IP model and lists the similarities and differences between both models.
TCP/IP Reference Model ExplainedThis tutorial is the fourth part of the article. It explains the five layers of the TCP/IP model in detail.
Data Encapsulation and De-encapsulation ExplainedThis tutorial is the fifth part of the article. It explains how data is encapsulated and de-encapsulated when it passes through the layers.
Purposes of OSI model
OSI model was created for the following purposes:-
- To standardize data networking protocols to allow communication between all networking devices across the entire planet.
- To create a common platform for software developers and hardware manufactures that encourage the creation of networking products that can communicate with each other over the network.
- To help network administrators by dividing large data exchange process into smaller segments. Smaller segments are easier to understand, manage and troubleshoot.
The layered approach
A layered approach is a hierarchical way to address all required technologies and devices in communication. It allows vendors and manufactures to build and design specific applications and hardware into one layer for a particular purpose without affecting the entire network protocol stack.
OSI model uses this approach. It divides the entire communication process into seven layers. Each layer describes a particular functionality along with the protocols and devices which are required to perform that functionality.
Advantages of the OSI Model
The advantages of the OSI Model are the following: -
- Help network administrators in determining the required hardware and software to build their network.
- Encourage hardware manufacturers to create networking products that can communicate with each other over the network.
- Provide a teaching tool to understand the communication process used between networking components.
- Separate a complex function into simpler components.
- Make troubleshooting easier, as network administrators can troubleshoot issues more quickly and effectively by looking in a layer that is causing the issue rather than finding it in the entire network.
Disadvantages of OSI Model
- It defines various services multiple times. For example, the error control service is defined in both Transport and Data Link layers.
- It does not allow layers to work parallel. A layer has to wait till it gets data from its predecessor layer.
- Instead of defining similar functions in the same layer, it defines them in different layers that add additional complexity.
- Instead of providing a summary of rarely used protocols and functions, it defines every protocol and function in detail that makes the model lengthy and less useful for administrators.
OSI Model in modern networks
Modern computer networks do not use the OSI model. They use the TCP/IP model. Despite this, almost all popular networking courses include the OSI model. There are two main reasons behind this. First, during the years in which many people thought the OSI model would become commonplace in the world of networking, many vendors, administrators, networking courses, and documents began to use terminology from the OSI model. That terminology remains today. Second, the OSI model describes every concept, function, and protocol in detail. Once you learn this model, you can easily learn the TCP/IP model by learning the difference between the two models.
In this tutorial, we will also follow the same path. First, we will understand the OSI model, and then we will understand how the TCP/IP model is different from the OSI model, and then we will understand the TCP/IP model in detail.
That’s all for this part. In the next part of this article, I will explain the seven layers of the OSI model in detail. If you like this tutorial, please don’t forget to share it with friends through your favorite social platform.