The OSI Model (Open Systems Interconnection Model) is a conceptual framework for describing the networking system’s functions. It was the first industry-standard paradigm for network communications, adopted in the early 1980s by all major computer and telecommunications corporations.
The present Internet is not built on the OSI paradigm, but rather on the more straightforward TCP/IP model. The OSI seven-layer model, on the other hand, is still extensively used because it aids in visualising and communicating how networks operate, as well as in isolating and troubleshooting networking problems.
Does OSI Model really matter?
The OSI Model is still very useful for debugging network problems, even if the modern Internet doesn’t fully follow it (it implements the simpler Internet protocol suite instead). This model can help decipher issues such as a single person being unable to access the internet, or a website being unavailable for thousands of people. A lot of extra labour can be avoided by narrowing the problem to one specific layer of the model.
How data flows through the OSI model?
Humans move information from network to network. In actuality, it crosses seven OSI layers in both sending and receiving devices. The application layer chooses a protocol and sends it to the presentation layer. Compress it and pass it to the session layer for communication setup.
The data is segmented and sent to the network layer for packet breaking. The data connection layer frames it and sends it to the physical layer. A bitstream of 1s and 0s is sent to the physical layer of the receiving device. The process repeats until the recipient opens the email.
The OSI Model’s lowest layer is concerned with electronically or optically passing raw unstructured data bits over the network from the sending device’s physical layer to the receiving device’s physical layer.
Data Link Layer
Directly linked nodes are utilised at the data link layer to execute node-to-node data transmission in which data is bundled into frames. Additionally, the data connection layer corrects any mistakes that happened at the physical layer.
The network layer is in charge of accepting frames from the data link layer and delivering them to their intended destinations depending on the frames’ addresses.
The transport layer is in charge of data packet delivery and error checking. It is responsible for controlling the size, sequencing, and ultimately the transport of data between systems and hosts. TCP, or Transmission Control Protocol, is a well-known example of the transport layer.
The session layer manages communications between machines. At layer 5, a session or connection between machines is established, managed, and terminated.
The presentation layer transforms or converts data for the application layer according to the application’s syntax or semantics. As a result, it is also referred to as the syntactic layer. Additionally, this layer is capable of handling the encryption and decryption operations necessary by the application layer.
Both the end user and the application layer communicate directly with the software application at this tier. This layer is responsible for the provisioning of network services to end-user apps such as a web browser or Office 365. The application layer is responsible for determining communication partners, resource availability, and communication synchronisation.
Application layer protocols comprise HTTP as well as SMTP (Simple Mail Transfer Protocol is one of the protocols that facilitates email communications) (Simple Mail Transfer Protocol is one of the protocols that enables email communications).