In this blog post, we'll focus on the steps of the OSI 7-layer model and how protocols are used to pass information.


A protocol is an internationally standardized commitment to accurately and reliably transmit information from a sender to a receiver in a communication situation. In order for these protocols to be applied in real-world communication situations, a standardized logical structure is required, the most representative of which is the OSI seven-layer model, which divides communication functions into seven stages. In this case, the information that the sender wants to send is sent through steps 1 through 7 of transmission and delivered to the receiver through steps 1 through 7 of reception.

Steps 5 through 7 of this model have in common that the information is being handled in software terms, which is called the upper layer. The topmost layer, level 7, is called the application layer, where the sender or software accesses the network. For example, this is where the sender accesses a site and logs in. The sixth layer, the representation layer, converts the information you want to send into computer-standard formats, such as strings and numbers, so that it's compatible with other computers. It also compresses the information during transmission and decompresses it during reception. Step 5, the session layer, adds checkpoints to the information you're sending to provide a reference point for resending in case of errors.

On the other hand, the first through fourth layers are called lower layers, but they all have in common that they function on the physical side to allow information to be delivered. The transport layer is responsible for breaking down the information into units called "frames," and then labeling each frame with the recipient's internet address to ensure that the information is delivered correctly. The third layer, the network link layer, is responsible for establishing the optimal path for the fastest and most secure delivery of the information to the recipient. Once the path is established, the second layer, the data link layer, converts the frame-by-frame information into bits, represented by binary 0s and 1s that can be physically transmitted, and sends them to the physical layer. Finally, the physical layer checks the mechanical conditions such as the type of cable and electrical signals to send the information, and if everything is in order, it sends the information over the cable.

In the process of transmitting and receiving this information, there is no direct connection between the N layers of the sender and the N layers of the receiver, except for the physical layers that are connected by cables. However, in order to accurately convey information, the n layers of the sender and receiver must functionally interact around the protocols of their respective layers, so each n layer of the sender must append the protocols of its layer to the information it sends. The protocols added by each layer are interpreted by the corresponding layer of the receiver and immediately discarded, leaving only the information that the receiver wants to receive in step 7.