The first part of a series of articles on the OSI network reference model.
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The second part of the article series examines the TCP/IP network model (DOD model), which consists of four layers. Their correspondence to the levels of the OSI model is described and why the TCP/IP model remains relevant in modern networks is explained.
Disclaimer: This article is intended for educational purposes. It explains the principles of the TCP/IP model and the role of the four-layer architecture in modern networks to help readers better understand the fundamentals of network interaction and its importance in the digital world.
The TCP/IP model is commonly referred to as the DOD (Department of Defense) model.
The DOD (or TCP/IP) model differs from the OSI network model in the number of layers.
Application level
Transport level (Transport)
Network layer (Internet)
Network access level (Network Access)
Surprisingly, four layers of DOD are enough to cover seven layers of the OSI model. Although there are certain differences. In general, if we do not go into details, the application layer of the DOD model corresponds to the three upper layers of the OSI model (application, presentation, session), the transport layer corresponds to the transport layer, and the network layer to the network, respectively, and the network access layer corresponds to the two lower layers of the OSI model ( data link, physical).
And if we go into details, we need to start with the fact that the TCP/IP network model was developed much earlier than the OSI model. The TCP/IP model was already formed on the basis of existing protocols, but OSI, on the contrary, first created a model, and then protocols for it, each of them has its own pros and cons. OSI is a more modern model, which is why it is discussed more often on the Internet, but the protocols used are the TCP/IP stack (groups, stacks (one on top of another)) based on the DOD model.
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