This tutorial explains in detail the similarities and differences between the OSI reference model and the TCP / IP model. In addition to that, it also explains the differences between the original TCP / IP model and the updated TCP / IP model.

OSI model vs TCP / IP model (which one is better and why TCP / IP is used instead of OSI)

TCP / IP and OSI are reference models of networking. The development of both models started in the early 1970s. Both were released in the 1980s. Manufacturers added support for one or both in their devices in the 1990s. In the late years 1990, the TCP / IP model became a common choice and the OSI model was rejected due to the slower formal standardization process compared to the TCP / IP model. The main manufacturers abandoned their proprietary networking models in favor of the TCP / IP model in the 2000s. Today, the world of computer networks uses only one network model and it is the TCP model. / IP.

Why is the OSI model always taught in networking courses?

In terms of explanation and documentation, the TCP / IP model is far from the OSI model. The OSI model is one of the best explained and best documented models ever created in the world of computer networks. It describes complex networking concepts, protocols and terms in a way that is not only easy to understand but also easier to remember.

Since the TCP / IP and OSI models were created to achieve the same goal, they both use the same set of open standard protocols and describe networking concepts in a similar fashion. By learning a pattern, you can easily learn the other pattern.

For this reason, even the OSI model is no longer supported and used by hardware manufacturers, but it is still taught in almost all networking courses. Once students have learned the OSI model, they are introduced with the TCP / IP model. As they have already learned the basic topics and layered approach of the OSI model, learning the TCP / IP model becomes much easier for them.

This article also follows the same approach. The first two parts of this article explain in detail the OSI model and its layers. This part explains the differences and similarities between the TCP / IP model and the OSI model and the following parts explain the TCP / IP model and its layers. Other parts of this article follow.

Similarities between the TCP / IP model and the OSI model

  • Both are logic models.
  • Both define networking standards.
  • Both provide a framework for creating and implementing standards and network devices.
  • Both divide the network communication process into layers.
  • In both models, a single layer defines a particular feature and sets standards for that feature only.
  • Both models allow a manufacturer to manufacture devices and network components that can coexist and work with devices and components made by other manufacturers.
  • Both models simplify the troubleshooting process by dividing complex functions into simpler components.
  • Instead of defining the standards and protocols already defined, the two models have referenced them. For example, Ethernet standards were already defined by the IEEE before the creation of these models. So, instead of redefining them, the two models used them as IEEE Ethernet standards.

Differences between the OSI model and the TCP / IP model

  • The OSI layer model has seven layers while the TCP / IP model has four layers.
  • The OSI layer model is no longer used while TCP / IP is still used in computer networks.
  • To define the functionality of the upper layers, OSI uses three separate layers (application, presentation and session) while TCP / IP uses only one layer (application).
  • Like the upper layers, OSI uses two separate layers (physical link and data link) to define the functionality of the lower layers while TCP / IP uses a single layer (link) for the same.
  • To define protocols and routing standards, OSI uses the network layer while TCP / IP uses the Internet layer.
  • Compared to the TCP / IP model, the OSI model is well documented and explains the standards and protocols in more detail.

Differences between the original TCP / IP model and the updated TCP / IP model

The TCP / IP model we use today is slightly different from the original TCP / IP model. The original TCP / IP model has four layers while the updated TCP / IP model has five layers.

The original version uses a single layer (Link layer) to define the features and components that are responsible for data transmission. The update version uses two layers for this (data link and physical).

The updated version divides the original Link layer based on functionality. The functionality that is directly related to physical transmission and the functionality that is indirectly related to physical transmission are specified in the physical layer and in the data link layer respectively.

In the updated version, the name of the Internet layer is replaced by the Network layer.

The following figure compares the OSI reference model to the original TCP / IP and updated TCP / IP models.

No matter which model you study or learn first, once you’ve learned one, you can easily correlate it with the others. In general comparison, the updated TCP / IP model is roughly similar to the OSI model with the exception of the application layer. For learning purposes, you may think that the application layer of TCP / IP does what the first three layers (application, presentation, and session) do in the OSI model.

That’s it for this part. In the next part of this article, I will explain in detail the TCP / IP model and its layers. If you like this tutorial, don’t forget to share it with your friends via your favorite social site.


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