History of OSI reference model, layers of osi reference model, about session, presentation, application, network,transport,datalink layers, responsibilities of osi reference model layers.

Layers of OSI reference model

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History of OSI reference Model

OSI reference model was developed by ISO (International Organization for Standardizing) before 20 years to achieve Open Interconnection between each system. Open Interconnection helps to work well under Multi vendor environment. Duty of OSI reference model is that will identity and align it into logically ordered layers and also helps to make all the functions work properly to define, dismantle a session between two computers. This model defines a structure for transferring the data between two computer systems that are shared with the same LAN or WAN. This model also identify functions which will be allowed by two machines from each other with no direct network connections.

Layers of OSI reference Model

OSI reference model can be categorized further into seven layers, Namely physical, data link, network, transport, session , presentation & application.

Physical Layer: This is called the first layer of OSI reference model, the duty of this layer to make sure that the transmission of the bit stream works fine. It receives frames from the Next layer Data link layer and transmits the content and structure in an organized way. Physical layer is responsible for all the incoming streams these streams are then passed on to data link layer Examples of transmission media are coaxial cabling, fibre optic cabling and also twist pair wiring.

Data link Layer:

This is the second layer of OSI reference model, it has two :sets of responsibilities they are Transmit and receive data. This data link layer should take care of giving end-to-end validity of data. While transmitting the data it also does packing instructions into frames.

Network layer

Network layer provide internetworking. The protocols in Network layer are responsible for finding out the route between the source and destination computers. This layer has its own disadvantage error detection/ correction mechanisms. It always relies upon end – to –end transmission service from the above two layers.

Transport Layer

This layer does similar job like data link layer, it is responsible to end-to-end reliability of transmissions. As compared to data link layer, transport layer can provide this service functionality beyond the Local LAN segment.

Session Layer Many protocols use this layer functionality into transport layer. Best example is RPC( Remote Procedure Calls)

The Presentation Layer

This layer helps in the process of translation between data encoding schemes such as ASCII and EBCDIC. It can also be used as a mediator between floating points formats.

Application Layer:

This is the top most layer of OSI reference model, aligning with its name Application layer, don’t think it contains any applications, it only acts as a good interface between applications and network services It can also initiate communication session.

These are the layers of OSI reference model This article is for educational purposes only.