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OSI Model


September 18, 2016
Published By : Pratik Kataria
Categorised in:


  • International standard organization (ISO) established a committee in 1977 to develop an architecture for systems communication.
  • Open System Interconnection (OSI) reference model is the result of this effort.
  • This model allows any two different systems to communicate regardless of their underlying architecture.
  • The OSI model describes how data flows from one computer, through a network to another computer.
  • The OSI model is not a protocol; it is a model for understanding and designing a network architecture that is flexible and robust.
  • The OSI model consists of seven separate but related layers, each of which defines a part of the process of moving information across a network.

Why so many layers?

  • To reduce the complexity, networks are organized as a stack of layers, one below the other.
  • Each layer performs a specific task,. It provides services to an adjacent layer.
  • Layers 1,2, 3- physical, data link and network are network support layers.
  • Layer 4, the transport layer, links the two subgroups.
  • Layers 5,6,7- session, presentation, and application are user support layers.