OSI Model | Open System Interconnection Layers | Computer Network OSI Model

OSI ( Open System Interconnection) Model:-

whenever we want to a data then firstly this data is generated by Network application, and actual data is transmitted by physical layer. so at sender end data is flow from application layer to physical layer and at receiver end data is flow from physical layer to application layer(as mentioned in below figure).

OSI Model | Pywix Classes

Application Layer:

Network applications produce the data, which has to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user. Ex: Application — Browsers, Skype Messenger etc.

Presentation Layer:

whenever we receive the data from application layer, it is not transferable. Presentation layer firstly translate this data so Presentation layer is also called the Translation layer. The functions of the presentation layer are :

  • Translation ( To make data transferable).
  • Encryption/ Decryption( For data security data is encrypted and decrypted by network application).
  • Compression( so that less bandwidth will require to transmit of data).

Session Layer:

This layer is responsible for establishment of connection, maintenance of sessions, authentication and also ensures security. The functions of the session layer are :

  • Session Establishment
  • Session Maintenance
  • Session Termination
  • Synchronization

Transport Layer:

The data in the transport layer is referred to as Segments. It is responsible for the End to End Delivery of the complete message. The transport layer also provides the acknowledgement of the successful data transmission and re-transmits the data if an error is found.

Transport layer receives the formatted data from the upper layers, performs Segmentation . It also adds Source and Destination port number in its header and forwards the segmented data to the Network Layer.

Transport Layer reads the port number from its header and forwards the Data which it has received to the respective application. The functions of the transport layer are :

Network Layer:

Network layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender & receiver’s IP address are placed in the header by the network layer. The functions of the Network layer are:

  • Routing( Decide the best path for data transmission)
  • Logical Addressing( Add IP address in data segment)

Originally published at https://pywix.blogspot.com.

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