The Open Systems Interconnection Model
An overview of the ISO/OSI Model of 7 Layers
OSI Model is a conceptual model which defines the seven layers of a computer system that uses to communicate over a network. It was the first standard model for networking paradigm embraced in the early 1980s by both large computers and telecommunications firms. OSI model is a tool to understand the data transferring flow in networks. It is composed of 7 ordered layers where each layer handles a specific job and communicates with the layers above and below itself. In this article, we’ll see about the OSI model, the Advantages of OSI, and its 7 layers.
Advantages of the OSI Model
- It allows network operators to divide big data exchanges into smaller segments.
- Due to layer separation, improvements or changes in one layer prevent the other layer from being affected.
- Identifying which network layer triggers a problem and concentrating efforts on it.
- Develop devices, software and, communication systems that allow open interoperability with products from any vendor.
- Reduces complexity and speeds up evolution.
Layers of the OSI Model
As mentioned above, the OSI Model is composed of 7 layers for data transmission.
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer
Let us look into the layers from the top to bottom as shown in the above image.
7. Application Layer
The Application layer is the topmost layer in the OSI model where the end users’ requests will start and response will end. This is the interaction layer of end-users through accessing network resources. This layer’s main function is to get end-user request and pass it to the next Layer (Presentation Layer).
6. Presentation Layer
The Presentation Layer is the layer in which the operating system operates with the data. In this layer, user request turns into more network-friendly form. This is also the layer where most translation, encryption, and compression of data will occur. Any data transmitted by the application layer is collected by the presentation layer for transmission throughout the session layer.
5. Session Layer
The Session layer manages sessions between two computers. It has the job of handling appropriate communication by managing while data is being transferred, establishing and terminating sessions when communication ends.
For instance, when two users are linked through a direct connection to each other, the session layer will handle authentication and authorization, decide the waiting time for responses, and making sure the connection between two computers is kept open as long as the communication ends.
4. Transport Layer
Handling the data is the main function of this layer. This layer will decide about breaking the appropriate size of data packets, send them at a proper rate, waiting for verification that the packets are being received and in the right order, flow control of data, sending data according to the connection speed of receiving device. Other than that this layer provides error control and reliable message delivery.
3. Network Layer
There are two main functions in this layer. One is breaking up data into network packets that are received from the transport layer and routing those network packets from source to correct destination. Internet protocol (IP) addresses will be used in this layer to route packets in the correct destination node. This layer is probably taking place outside of our device and inside our router, where we get closer to the physical layer.
2. Data Link Layer
Data Link Layer defines the format of the data on the network. This layer will break up packets that are received from the network layer and send them for the physical layer to use. There are two parts to this layer. Those are Logical Link Control (LLC) and Media Access Control (MAC). LLC recognizes network protocols, handles error corrections, and synchronizes frames. MAC allows permission to transfer and receive data.
1. Physical Layer
Last Layer of OSI Model. The physical layer is responsible for the connection of physical components between network nodes. Such as the connector, the electrical cable like Ethernet and fiber cables, or wireless technology connecting devices like Wi-Fi. In this layer, information is broken into bits and transmit from one physical port to another through a transmission medium.
Thank you for reading, hope it helps!
References
1. https://youtu.be/vv4y_uOneC0
2. https://www.imperva.com/learn/application-security/osi-model/
Thumbnail: https://network-byte.com/osi-model-a-7-layers-architecture/
