• What is the OSI model?
• Background of the OSI model
• How does the OSI model work?
• What is the OSI model for?
• Layers of the OSI model

We explain what the OSI Model used in computer networks is, and how it works. Also, what is it for and what are its layers.

The OSI model allows communication between different computer networks.

What is the OSI model?

The OSI Model (from the acronym in English: Open Systems Interconnection, that is, "Interconnection of Open Systems"), is a reference model for protocols communication of computer networks or computer networks. It was created in the 1980s by the International Organization for Standardization (ISO).

The OSI Model was initially published by the International Telecommunications Union (ITU) until 1983, and since 1984 it has also been offered by ISO itself, with a standard. Its function was to standardize or serialize communications on the Internet, since in its beginnings it was extremely chaotic.

Being a normative model, the OSI Model is really a theoretical construct, with no direct correlation in the world of the tangible. It is nothing more than an attempt to regulate the diverse and varied technological voices of the world, since there are numerous manufacturers, companies and technologies in the world of telecommunications.

This model has been refined over time and today offers seven different layers with which to define the different phases that the information on your journey from one electronic device to another connected on the network. No matter the geographical location of the user or the type of technology used, all global interconnection means, such as Internet, use this type of unified protocols.

Background of the OSI model

The development of computer networks and their expansion in the early 1980s revealed the need to interconnect systems from various origins, or the networks that they formed and maintained. As with people who speak different languages, telecommunications were unable to continue its expansive path.

Even programs designed for networking had problems with each other, since copyright rules on computerized design were an additional barrier.

The idea of ​​creating the OSI Model as a solution to this problem arose after the ISO carried out a research in the matter. Thus, ISO set out to determine the general set of rules applicable to all networks.

How does the OSI model work?

The operation of the OSI Model depends directly on its seven layers, in which it breaks down the complicated process of digital communication. By compartmentalizing it, it assigns very specific functions to each layer, within a fixed hierarchical structure.

Thus, each communication protocol uses these layers in their entirety or only some of them, but by obeying this set of rules, it guarantees that communication between networks is efficient and, above all, that it takes place on the same terms.

What is the OSI model for?

The OSI Model is fundamentally a conceptual tool for organizing telecommunications. It universalizes the way in which information is shared between computer networks or computerized systems, regardless of its geographical origin, business or other conditions that could make it difficult for data to communicate. data.

The OSI Model is not a network topology, nor is it a network model per se, nor is it a protocol specification; It is simply a tool that defines the functionality of the protocols, to achieve a communication standard, that is, to achieve that all the systems speak the same language. Without it, a network as vast and diverse as the Internet would be practically impossible.

Layers of the OSI model

Each layer has specific functions to ensure communication.

The seven layers or levels of the OSI model are as follows:

• Physical layer. The lowest layer of the model is responsible for the network topology and the global connections between the computer and the network, referring to both the physical environment and the way in which information is transmitted. It fulfills the functions of specifying information about the physical medium (types of cable, microwaves, etc.), defining information about voltage electric transmission, the functional characteristics of the network interface and guarantee the existence of a connection (although not its reliability).
• Data link layer. It deals with physical rerouting, error detection, media access, and flow control during communication, being part of the creation of basic protocols to regulate the connection between computer systems.
• Network layer. It is the layer that is responsible for identifying the existing routing between the networks involved, thus, the data units are now called "packets" and can be classified according to the routing protocol or routable protocol they use. The former select the routes (RIP, IGRP, EIGRP, among others) and the latter travel with the packets (IP, IPX, APPLETALK, etc.). The objective This layer is to ensure that data reaches its destination, even if it involves using intermediate devices, such as routers or routers.
• Transport layer. This is where the data found within each package is transported, from the source to the destination computer, regardless of the physical medium used for it. Its work is done through logical ports and shapes the so-called Sockets IP: Port.
• Session layer. It is responsible for controlling and maintaining the link between the computers that exchange data, ensuring that, once communication between both systems is established, the data transmission channel can be resumed in case of interruption. These services they can become partially or totally dispensable, depending on the case.
• Presentation layer. This layer deals with the representation information, that is, its translation, ensuring that the data received at any end of the network is fully recognizable, regardless of the type of system used. It is the first layer that deals with the content of the transmission, rather than the way it is established and sustained. In addition, it allows the encryption and encoding of the data, as well as its compression, its adaptation to the machine that receives it (a computer, a tablet, a cell phone, etc.).
• Application layer. As new communication protocols are continually being developed, as new applications emerge, this last layer defines the protocols that applications use to exchange data and allows them to access the services of any of the other layers. Generally, this whole process is invisible to the Username, who rarely interacts with the application level, but with programs that interact with the application level, making it less complex than it really is.

The layers of the OSI Model can be remembered through the FERTSPA mnemonic rule: Physics, Data Link, Network, Transport, Session, Presentation and Application.