OSI reference model

OSI Reference Model

What is the simplest explanation of the OSI model involving real examples?

• OSI long from is open loop system interconnection.
• It is developed by International Standard Organization (ISO) in 1970.
• OSI reference model has 7 layers.
• Physical (layer 1), Data link (layer 2), Network (layer 3), Transport (layer 4), Session (layer 5), Presentation (layer 6), Application (layer 7).
• Below mention the functions that occur at each layer of the OSI model.

OSI reference model

Application layer:

• The application layer of the OSI model marks the spot where user actually communicate or interact with the computer.
• User application is in any form like file, print, images, messages, database, and application services.
• Data an application layer is in original from.

Presentation layer:

The Presentation layer gets its name from its purpose it present data to the application layer and is responsible for data translation and code formatting. A successful data transfer technique is to adapt the data into a standard format before transmission.

Computer are configured to receive this generically formatted data and then converted it back into its native format for reading for exam, from EBCDIC to ASCII. By providing translation services, the presentation layer ensures that the data transferred from one system. Application layer can be read and understood by application layer on another’s.
The OSI has protocol standards that define how the data should be formatted task like data compression, decompression, encryption, and decryption are all associated with this layer. Presentation layer standards are even involved in multimedia operation.

• Presentation layer perform data encryption at sender side and decryption done at receiving side .
• It is an user interface layer user can do compression of data at sender side and decompression was happened at receiver side.
• User can mange data in appropriate from.
• Data an presentation layer is in bit from.

Session layer:

The Session layer is responsible for setting up, managing, and then tearing down sessions between between presentation layer entities. This layer also provides dialog control between devices, or nodes. It coordinates communication between systems and servers to organize their communication by offering three different mods: simplex, half duplex, full duplex. To sum up, the session layer basically keeps applications data separate from other application data,

• Session layer perform flow control of data.
• Session layer provide session management.
• Session layer also mange header size.
• Session layer also main tented data and time user sending and receiving data.

Transport layer:

The Transport layer segments and reassembles data into stream. Services located in the transport layer handle from upper layer application and unite it onto the same data stream. They provide end to end data transport services and can establish a logical connection between the sending host and destination host on an internetwork,
The Transport layer the sending host for providing the mechanisms for multiplexing upper layer application, establishing virtual connections, and tearing down virtual circuits. It also hides the many and sundry details of any network dependent information from the higher layer facilitating data transfer.

• Transport layer convert the bit into segment.
• It assign the sequencing to the every segment.
• It also done port addressing.
• It perform connection management.
• UDP and TCP is used for connection management.

Network layer:

•  It routes the signal through different channels from one node to other.
•  It acts as a network controller. It manages the Subnet traffic.
•  It decides by which route data should take.
•  It divides the outgoing messages into packets and assembles the incoming packets into messages for higher levels.

Data link layer:

• Data link layer synchronizes the information which is to be transmitted over the physical layer.
• The main function of this layer is to make sure data transfer is error free from one node to another, over the physical layer.
•  Transmitting and receiving data frames sequentially is managed by this layer.
•  This layer sends and expects acknowledgements for frames received and sent respectively. Resending of non-acknowledgement received frames is also handled by this layer.
•  This layer establishes a logical layer between two nodes and also manages the Frame traffic control over the network. It signals the transmitting node to stop, when the frame buffers are full.

Physical layer:

•  Big picture of communication over network is understandable through this  OSI model.
•  We see how hardware and software work together.
•  We can understand new technologies as they are developed.
•  Troubleshooting is easier by separate networks.
•  Can be used to compare basic functional relationships on different networks.

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