OSI Model Levels

The multi-level OSI model is very important for understanding how machines interact with each other. In this article, we will look at the basics of the OSI model and describe the levels of interconnection of various systems with each other.

The layers help the network specialist visualize what is happening in the networks, and also help to identify the source of the problem in the network – at the software or hardware level.

The OSI model also helps the application developer determine which layers he needs to work with. Technology providers often rely on the OSI model to help customers understand the level at which their products work.

What is the OSI model?

OSI (Open Systems Interconnection) is a conceptual model of open systems interaction that combines all communication functions of computing or telecommunication systems. OSI demonstrates how computers or other types of systems communicate with each other.

Since each system has its own technological features and works with different telecommunication protocols, it can be very difficult to put it on a par with a system with the same characteristics. That’s why we need the OSI model — to create a universal standard for communication between devices. For example, OSI allows us to send an email from a mobile device to a desktop PC and vice versa.

The OSI model consists of 7 interdependent layers (levels), each of which describes the path of data from one machine to another. Each layer performs certain functions that solve data transmission problems, such as physical addressing, access control, routing, data reassembly, and more. We will get to know them in the article. The OSI model consists of the following levels:

Level 1: Physical.

Level 2: Data link.

Level 3: Network.

Level 4: Transport.

Level 5: Session.

Level 6: Presentation level.

Level 7: Applied (Application).

The physical, link, and network layers are considered environment layers because they are hardware-oriented (i.e., each function is handled by hardware). Transport, session, presentation, and application layers are considered host layers because they are software-oriented.

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