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O.S.I REFERENCE

April 3, 2009 1 comment

OSI Reference Model : A networking reference model defined by the ISO (International Organization for Standardization) that divides computer-to-computer communications into seven connected layers. Suchlayers are known as a protocol stack. Each successively higher layer builds on the functions of the layers below, as follows:

  • Application layer :The highest level of the model. It defines the manner in which applications interact with the network, including database management, e-mail, and terminal-emulation programs.
  • Presentation layer : Defines the way in which data is formatted, presented, converted, and encoded.
  • Session layer : Coordinates communications and maintains the session for as long as it is needed, performing security, logging, and administrative functions.
  • Transport layer : Defines protocols for structuring messages and supervises the validity of the transmission by performing some error checking.
  • Network layer : Defines protocols for data routing to ensure that the informationarrives at the correct destination
  •  Data-link layer : Validates the integrity of the flow of data from one node to another by synchronizing blocks of data and controlling the flow of data.
  • Physical layer : Defines the mechanism for communicating with the transmission medium and interface hardware.
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