Introduction to the ISO OSI model


Introduction to the ISO OSI model:

OSI model based on data communication and network.
Before 1990 was the Open Systems Interconnection OSI model. Everyone believes
That OSI model will be the ultimate standard for data communication, but
This does not happen. The TCP|\IP suite has become a major enterprise architecture
Because it is widely used and tested on the Internet; the OSI model is
Never fully realized.
There are many users who use computer networks all over the world. Ensure that ISO national and global communications (ISO on behalf of the International Organization for Standardization) develop this model. This is called the Open Systems Interconnection (OSI) model, commonly known as the OSI model. The architecture of the OSI model consists of seven layers. It defines seven layers or levels in a complete communication system.

OSI model

Application layer

The application layer is a platform.That provide platform for sending and receiving data over the network. All applications and utilities that communicate with the network belong to this layer.
Examples of
Browser: -Firefox, Internet browser, Google Chrome, etc.
Customers by email: -Prospect Express, Mozilla Thunderbird, etc.
FTP client: -FileZilla, SFTP, vsftp.

Presentation layer

The presentation layer prepares the data. It gets data from the application layer and marks them with format codes such as. doc ,. jpg ,. txt ,. avi, etc. These file extensions allow you to easily recognize.That a particular file is formatted with a specific type of application. Use the format presentation layer to also handle compression and encapsulation.Whenever it compresses (in the sender computer) the reconciliation (in the receiving computer) the data file. This layer can also encapsulate data, but it is rare because it can be done more efficiently by lower layers.

Session layer

The session layer processes the connection. It establishes, manages and terminates sessions between two communication nodes.However this layer provides services for the presentation layer. However the session layer also synchronizes conversations between the presentation levels of two hosts and manages their data exchange. For example, a web server may have many users communicating with the server at a given time. Therefore, it is important to follow the users who communicate on which path,therefor the session layer accurately manages this responsibility

Transport layer

The main purpose of the transport layer. Transfer the complete message from the source to the destination. In fact the transport layer ensures that the entire message arrives intact, providing error control and flow control at the source at the target level. In fact it determines whether the data transfer must be on a parallel path or on a single path.
The transport layer breaks down messages (data) into small units. So that they can be managed more efficiently through the network layer. And ensure that messages arrive in an orderly manner through error checking and flow control .

Network layer

The main purpose of this layer is to transfer packets from the source to the destination via multiple links (networks). The network layer is responsible for providing a logical address called an IP address. Routers work on this layer. The main functions of the layer are:
• Set the IP address
• Find routes based on IP addresses to reach their destinations
• Connect different types of data links, such as Token Ring, Serial, FDDI, Ethernet, etc.

Data link

• The data link layer is the most reliable node for the node to transmit data. It forms frames from packets received from the network layer. Its provides them to the physical layer. It also synchronizes the information that will pass through the data transfer. The error check is easy to complete. The coded data transmitted to the physical.
• The data link layer uses error detection bits. It also corrects the error. In fact outgoing messages are assembled in frames. The system then waits to receive confirmation after transmission. The sending of messages is reliable.

Physical layer

The physical layer manages the communication media.In fact this layer receives images from the data link layer and converts them into bits. When it loads these bits on the actual communication medium. Depending on the media type. These binary values ​​are converted in the signal. Some use audio tones, while others use state transitions-from top to bottom.


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