OSI Model in Computer Network
What is OSI Model in Computer Network
The Open Systems Interconnection (OSI) model is a conceptual model created by the International Organization for Standardization which enables diverse communication systems to communicate using standard protocols. In plain English, the OSI provides a standard for different computer systems to be able to communicate with each other.
The OSI model can be seen as a universal language for computer networking. It’s based on the concept of splitting up a communication system into seven abstract layers, each one stacked upon the last. Each layer of the OSI model handles a specific job and communicates with the layers above and below itself.
OSI stands for Open Systems Interconnection. It has been developed by ISO – International Organization of Standardization, in the year 1984. It is a 7 layer architecture with each layer having specific functionality to perform. All these 7 layers work collaboratively to transmit the data from one person to another across the globe.
Characteristics of OSI Model
- The OSI model is divided into two layers: upper layers and lower layers.
- The upper layer of the OSI model mainly deals with the application related issues, and they are implemented only in the software. The application layer is closest to the end user. Both the end user and the application layer interact with the software applications. An upper layer refers to the layer just above another layer.
- The lower layer of the OSI model deals with the data transport issues. The data link layer and the physical layer are implemented in hardware and software. The physical layer is the lowest layer of the OSI model and is closest to the physical medium. The physical layer is mainly responsible for placing the information on the physical medium.
Functions of the OSI Layers
There are the seven OSI layers. Each layer has different functions. A list of seven layers are given below;
- Physical Layer
- Data-Link Layer
- Network Layer
- Transport Layer
- Session Layer
- Presentation Layer
- Application Layer
Physical Layer
An application that communicates with other computers that corresponds to the application's communication service.
Data Link Layer
It defines how to transfer data on a single link.
Network Layer
This layer defines the end-to-end packet transport, which defines the logical addresses that identify all nodes and also defines how the routes are implemented and how they are learned.
Transport Layer
The functions of this layer include whether to choose the error recovery protocol or the error-free recovery protocol, and multiplex the input of different application data streams on the same host, and also include the function of reordering received packets that are not in the correct sequence.
Session Layer
It defines how to start, control and end a session, including the control and management of multiple bidirectional messages so that applications can be notified when only a portion of a continuous message has been completed, so that the data seen by the presentation layer is contiguous, In some cases, if the presentation layer has received all of the data, the data represents the presentation layer.
Presentation Layer
The main function of this layer is to define the data format and encryption.
Application Layer
An application that communicates with other computers that corresponds to the application's communication service.