What is the OSI Model, and how does it work?

 

What is the OSI Model, and how does it work?

OSI - Open Systems Interconnection

               1. The Open Systems Interconnection (OSI) model is a virtual model for describing the internal structure and technologies of a computer system.

               2. Network communication is divided into seven tiers according to the OSI Model. These layers are helpful in detecting network problems.

               3. A lot of unneeded work can be avoided if the problem can be focused down to one specific layer of the model.

Seven layers of the OSI Model

7. Application layer

               1. In the OSI model, the Application Layer is the layer closest to the end user.

               2. It receives data directly from users and shows the information to them.

               3. Web browsers and email clients, for example, rely on the application layer to establish communications.

               4. Client software programmes, on the other hand, should not be considered part of the application layer.

               5. The protocol and data processing that the software relies on to display relevant data to the user are handled by the application layer.

               6. HTTP and SMTP are examples of application layer protocols.

[HTTP - HyperText Transfer Protocol, SMTP - Simple Mail Transfer Protocol ]

6. Presentation layer

               1. The presentation layer is in charge of data compression, encryption, and translation.

               2. In general, it refers to the process of preparing or translating application format to network format, or network formatting to application format.

               3. Layer 6 is responsible for applying encryption on the sender's end and decoding encryption on the receiver's end so that it can offer the application layer with unencrypted, readable data if the devices are interacting via an encrypted connection.

               4. By reducing the amount of data exchanged, this aids in improving communication speed and efficiency.

5. Session layer

               1. A session is generated at the Session Layer when two computers or other networked devices need to communicate with one another.

               2. This layer is in charge of establishing and maintaining communication between the two devices.

               3. The session is the period of time between when a communication is initiated and when it is ended.

               4. Data transport is also synchronised with checkpoints by the session layer.

               5. For instance, if a 100 megabyte file is being transferred, the session layer could set a checkpoint every 5 megabytes.

               6. If a disconnect or crash occurs after 52 megabytes have been transferred, the session can be continued from the previous checkpoint, requiring only 50 megabytes of data to be transferred.

               7. The entire transfer would have to be restarted from the beginning if the checkpoints were not present.

4. Transport layer

               1. The end-to-end communication between the two devices is handled by 4th Layer.

               2. Before transferring data to layer 3, data from the session layer is broken up into segments and sent to layer 3.

               3. The receiving device's transport layer is in charge of reassembling the segments into data that the session layer may use.

               4. Flow control and error control are also handled by the transport layer.

               5. On the receiving end, the transport layer performs error control by confirming that the data received is full and, if it isn't, requesting a retransmission.

3. Network layer

               1. The network layer is in charge of making data transit between two networks easier.

               2. If the two communicating devices are on the same network, the network layer isn't required.

               3. On the sender's device, the network layer breaks up segments from the transport layer into smaller pieces called packets, which it then reassembles on the receiving device.

               4. Routing is a function of the network layer that determines the optimum physical path for data to take to reach its destination.

2. Data link layer

               1. The data connection layer is similar to the network layer in that it allows data to be sent between two devices on the same network.

               2. The data link layer decomposes packets from the network layer into smaller units known as frames.

               3. In intra-network communication, the data link layer, like the network layer, is responsible for flow control and error control.

1. Physical layer

               1. The physical equipment used in data transfer, such as cables and switches, are included in this layer.

               2. This layer is also where data is turned into a bit stream, which is a string of 1s and 0s.

               3. Both devices' physical layers must agree on a signal protocol so that the 1s and 0s can be identified on both devices.

OSI Model's Data flow

               1. The OSI model has been chastised for its inherent implementation complexity, which makes networking operations inefficient and time-consuming.

               2. The scholarly approach to building the OSI protocol suite was to replace current protocols with improved ones at all communication tiers.

               3. This strategy failed to gain popularity in the market since companies had already spent large resources in TCP/IP products and had to handle interoperability with the OSI model's vast array of protocols and specifications.

               4. Likewise, academia saw the OSI model as a politically motivated invention by European telecommunications and US government officials.
In real-world network situations, the previous TCP/IP architecture model has already established itself.

               5. It provided a stable foundation for the Internet, addressing all security, privacy, and performance concerns.

              6. The OSI model's continued study and development, investments, and industry-wide adoption could have made today's cyber world a different (and perhaps better) place, but the TCP/IP model's pragmatism delivered us the internet we have today.