OSI Model

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 OSI model 



The International Organization for Standardization (IOS) developed the open systems interconnection (OSI) model, a conceptual framework that enables various communication systems to exchange data via agreed-upon protocols. The OSI, or Open Systems Interconnection, offers a standard for various computer systems to be able to communicate with one another. One could think of the OSI Model as a common language for computer networking. Its foundation is the idea that a communication system may be broken down into seven abstract levels, each one built on top of the previous.

Relevance Of The OSI Model

The OSI Model is still very helpful for diagnosing network issues even though the modern Internet doesn't precisely adhere to it (rather, it closely follows the less complex Internet protocol suite). The OSI Model can assist in deconstructing the issue and identifying the troubleshooting step, whether it concerns one person who is unable to connect their laptop to the Internet or a website that is unavailable to thousands of users. A lot of pointless labor can be avoided if the issue is limited to a single layer of the model.


Various Layers of OSI Model

7. Application Layer

The only layer that works directly with user data is this one. The application layer is required for communication initiation by software programs like web browsers and email clients. But it should be made clear that client software programs do not belong in the application layer; rather, the application layer is in charge of the protocols and data manipulation that the software depends on to give the user relevant data. Protocols used at the application layer include HTTP and SMTP (Simple Mail Transfer Protocol is one of the protocols that enables email communications).

6. The presentation layer

The area that is unrelated to data representation at the application layer is represented by the Presentation Layer. In general, it denotes the preparation, translation, or conversion of application format to network format or vice versa. To put it another way, the layer "presents" data to the network or the application. Data encryption and decryption for safe transmission is an excellent illustration of this; this takes place at Layer 6.

5. Session Layer

The session layer establishes sessions, or channels of communication, between devices. It is in charge of starting sessions, making sure they are active and open while data is being exchanged, and shutting them down once communication is complete. The session layer can also establish checkpoints during a data transmission, allowing devices to pick up where they left off in the event that the session is terminated.


4. The transport layer
The coordination of data transit between hosts and end systems is handled by the transport layer. How much information should be sent, at what speed, and to where? The Transmission Control Protocol (TCP), which is constructed on top of the Internet Protocol (IP), often known as TCP/IP, is the most well-known example of the Transport Layer. IP addresses operate at Layer 3, the Network Layer, whereas TCP and UDP port numbers operate 

3. The network layer

Data transfer between two distinct networks is made possible by the network layer. The network layer is not required if the two communicating devices are on the same network. On the sending device, the network layer divides transport layer segments into smaller pieces, known as packets, and reassembles these packets on the receiving device. Routing is the process by which the network layer determines the optimum physical route for the data to take to get to its destination.

2. Data Link Layer

The data link layer creates and breaks connections between two network nodes that are physically close to one another. Frames are created from packets, which are then sent from source to destination. This layer is made up of two components: Media Access Control (MAC), which utilizes MAC addresses to connect devices and specifies permissions to transmit and receive data, and Logic Link Control (LLC), which identifies network protocols, does error checking and synchronizes frames.

1. The physical layer

The physical tools used for data transfer, like as cables and switches, are included in this layer. This layer is also where the data is transformed into a bit stream or a series of ones and zeros. For the 1s and 0s on both devices to be distinguishable from one another, the physical layer of both devices must also agree on a signal protocol.


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