OSI Model (Meaning and Explanation)

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.

What is the OSI model?

The OSI Model (from the acronym in English: Open Systems Interconnectionthat is, “Open Systems Interconnection”), It is a reference model for communication protocols in 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 given that in its beginnings it was extremely chaotic.

Being a normative model, the OSI Model It's really a theoretical construct without 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, given that 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 information goes through on its journey from one electronic device to another connected on the network. No matter the geographic location of the user or the type of technology used, all means of global interconnection, such as the Internet, use this type of unified protocols.

Background of the OSI model

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

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Even programs designed for interconnection had problems with each other as copyright rules on computerized design posed an additional barrier.

The idea of creating the OSI Model as a solution to this problem arose after the ISO carried out research on the matter. So, 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, into which the complicated process of digital communication is broken down. By compartmentalizing it, it assigns each layer very specific functions, 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, ensures that communication between networks is effective and above all that it occurs on the same terms.

What is the OSI model for?

The OSI Model is fundamentally a conceptual tool for organizing telecommunications. Universalizes the way information is shared between computer networks or computerized systems, regardless of their geographic or business origin or other conditions that could hinder the communication of data.

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

OSI Model Layers

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 medium and the way in which information is transmitted. It fulfills the functions of specifying information about the physical medium (cable types, microwaves, etc.), defining information about the electrical voltage of the transmission, the functional characteristics of the network interface and guaranteeing the existence of a connection ( although not its reliability).
Data link layer It deals with physical redirection, error detection, access to the medium 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 routing that exists between the networks involved, thus, the data units become known as “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 goal of this layer is to ensure that data reaches its destination, even if this means using intermediate devices, such as routers or routers.
Transport layer This is where the transport of the data found within each packet is carried out, from the source computer to the destination computer, regardless of the physical medium used for it. Its work occurs 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 if it is interrupted. These services may become partially or totally dispensable, depending on the case.
Presentation layer This layer deals with representation of the information, that is, its translation, guaranteeing that the data received at any end of the network is completely recognizable, regardless of the type of system used. It is the first layer that deals with the content of the transmission, rather than how the transmission is established and sustained. In addition, it allows the encryption and coding of data, as well as its compression, its adaptation to the machine that receives it (a computer, a tablet, a cell phone, etc.).
Application layer Since new communication protocols are continually developed as new applications emerge, this last layer defines the protocols that applications use to exchange data and allows them to access services from any of the other layers. Generally, this entire process is invisible to the user, who rarely interacts with the application level, but rather with programs that interact with the application level, making it less complex than it really is.