Translation: What is the OSI Model?

The term OSI stands for Open System Interconnection, which is a conceptual model that divides the process of communication in a network and the transfer of data through it into seven fundamental layers. The purpose of this is to organize the communication process between the network layers and between the sender and receiver in a thoughtful and organized manner. It facilitates dealing with the network and troubleshooting errors that may occur during the communication process. This model is the reference framework for all companies dealing with networks and communications in building their systems and networks; it is globally recognized. The OSI model was adopted in the early 1980s by companies and institutions that rely on networks to build their systems and perform their operations. The OSI model can be considered the language used with computer networks within a set of standardized protocols divided into layers, regulating the rules of communication in the network.

Benefits and Importance of the OSI Model:

As mentioned earlier, its primary goal is to create a comprehensive and organized reference for building networks, understanding, and improving the communication process between connected devices within the network.

The benefits of this model can be divided into several points:

- Common System Among Organizations: The OSI model is a globally recognized model that allows network engineers worldwide to deal with any network within the OSI model, which serves as the main reference for all companies and institutions globally. It provides a unified understanding among network operators, making it easy to work with the network by dividing it into 7 conceptual layers that are easy to handle.

- Speed in Development: The model contributes to enabling network engineers to understand the network better, faster, and with good accuracy. This makes it easy to operate the network, providing speed in performance, implementation, reliability, higher security, and ease in troubleshooting problems that may arise in the network. This ease facilitates the ability to expand the network's performance and work on its development, enabling it to provide greater advantages within the network in a unified and easy-to-understand model that enhances network performance and makes it easier to build, develop, and expand as desired.

- Network Task Division and Standardization: The OSI model separates network communication tasks and data transfer through 7 layers, with each layer responsible for specific tasks and functions programmed to work with them. After each layer completes its required task, it transfers the data or information or whatever the output type from the specified layer to the next layer in an organized and defined manner. These layers are divided into lower and upper levels, working in both directions from top to bottom and from bottom to top. In other words, the sender can also be a receiver, reflecting the layer functions according to its state. The same applies to the receiver if it wants to be a sender.

OSI Model Layers:

- Physical Layer: The first layer responsible for connecting physical communication media that transfer data in the network as digital and electronic signals through physical communication media such as copper cables or optical fibers, and also through the air via wireless communication. Examples of technologies or devices used in this layer include network cards. This layer is closely related to Bluetooth and NFC technologies.

- Data Link Layer: The second layer that manages data frames forming digital signals in a set of data packets, dividing data packets into frames. The purpose of this layer is to control data flow and check for errors within it. Sub-layers under this layer include LLC (Logical Link Control) and MAC (Media Access Control).

- Network Layer: The third layer in the lower layers of the network, which adds the sender and receiver's addresses and performs routing operations. This layer divides segments into data packets, and they are reassembled at the receiving end. Devices such as routers operate within this layer, determining the best path on the network for data transfer. IPv4 and IPv6 are essential protocols used in this layer, along with IP and IPX.

- Transport Layer: The fourth layer in the middle of the network, responsible for secure data transfer within the network by verifying the sending and receiving of data from the sender to the receiver. It checks for errors in the sent message and data within its basic operations. Data is assembled into a group of segments here. TCP protocols are used to control data transmission with loss-free connections, and the UDP protocol retains less important data packets, which may result in data loss. TCP/IP protocols are also used here.

- Session Layer: The fifth layer in the upper layers, responsible for coordinating the communication process between two separate applications and setting up the communication process between them. Protocols such as NFC and SMB are commonly used in this layer. This layer establishes communication paths between two different devices to initiate communication between them by opening or closing communication paths.

- Presentation Layer: The sixth layer in the upper layers, responsible for the structure and format of data. It transforms data into computer-understandable data, compresses and decompresses data, and receives it correctly when decompressed. It also performs data encryption. Modeling languages such as HTML, CSV, and JSON are used in this layer to describe data.

- Application Layer: The seventh and final layer in the upper layers, responsible for communication operations within a specific application. It includes email and messaging services. Consideration is given to the type of connection, such as HTTP or HTTPS, in addition to protocols like POP3 and SMTP.

Operation of the OSI Model:

- When sending data from the sender, the application layer passes the data communication to the layers below it.

- Before passing the communication, headers and specific addresses are added to the data.

- The session layer opens the communication process between the sending party and the destination address.

- Checking data for errors from the transport layer to the lower layers.

- Working on processing data and checking the headers and addresses within the lower layers.

- Receiving data at the receiving end, notifying the sender of the completion of the sending process, and its arrival at the other party.

Interaction Methods Between Parties in the OSI Model:

- Simplex (one way): A method where there is only one path, either a sender or a receiver.

- Half Duplex: A turn-based system where there is a sender and a receiver, but only one at a time.

- Full Duplex:The most commonly used system in networks where dialogue is alternated between network parties at the same time, meaning that sending and receiving operations occur simultaneously.