The OSI model was created by the ISO.
The concept of model comes from the Italian model , coming from the Vulgar Latin modellus (which is the diminutive of the Latin modŭlus , translatable as "measurement" ). The term can refer to an example, archetype or prototype that functions as a reference for its reproduction or imitation .
The outline of a certain reality or a system that is created to promote an analysis or promote the understanding of something is also called a model.
OSI , meanwhile, is the acronym corresponding to the English expression Open Systems Interconnection (which can be translated as Open Systems Interconnection ). The notion is used by the International Organization for Standardization ( ISO , or International Organization for Standardization in our language ).
What is an OSI model
The OSI model was devised by the ISO to promote communication between different systems. In this way, it uses standard protocols to enable the connection of the networks that link the equipment.
The OSI model is understood as a kind of universal language that is structured by dividing systems into seven abstract layers. Each layer is positioned on top of the previous one, fulfilling a specific function.
The main advantage that the OSI model offers is that it helps detect problems and allows the isolation of the layer in which the failure occurs. By separating the source of the problem from the rest of the layers, you save time in the resolution effort.
The OSI model is structured in seven layers.
The seven layers
The physical layer is the basis of the OSI model . This is the first layer or the bottom layer, if the structure is considered in an ascending direction. This physical layer, which is made up of the equipment that participates in the transmission of data, makes it possible to convert the data into sequences of bits.
Then appears the data link layer , which is responsible for the transmission of data between computers that are part of the same network . What it does is divide the packets into frames. Continuing with the OSI model , it continues with the network layer that transfers data between different networks, divides the segments into packets and carries out routing.
The transport layer is the fourth layer, responsible for communicating two devices end to end. The development of the OSI model continues with the session layer (which opens and closes communications between devices ), the presentation layer (which prepares the data for consumption) and finally the application layer (which engages in direct interaction with the devices). user data).
It can be said that email clients and web browsers depend on this seventh layer. The SMTP and HTTP protocols, for example, fall under the application layer.
Data transmission in the OSI model
The transfer of information that is understandable to people in a network of devices has to go through all the layers of the OSI model . First the route is performed in a descending direction and then it is completed in ascending order.
Suppose that Juan wants to send an email to Mariana . Juan accesses his email application, writes the text and clicks "Send" . The application thus forwards the message to the application layer, which chooses the protocol and transmits the data to the presentation layer.
The presentation layer performs compression on the data and sends it to the session layer, which begins the communication session. The data arrives at the transport layer, where it is segmented and then segmented again at the network layer and once again at the data layer. The resulting frames are sent by the link layer to the physical layer, which is responsible for converting them into a sequence of bits that is transmitted over a physical medium.
There, Juan 's message reaches Mariana 's system. Then the journey through the layers of the OSI model begins but in the reverse order.