The OSI Reference Model

Basically, the ISO is pretty much the Emily Post of the network protocol world. Just as Ms. Post wrote the book setting the standards—or protocols—for human social interaction, the ISO developed the OSI reference model as the precedent and guide for an open network protocol set. Defining the etiquette of communication models, it remains today the most popular means of comparison for protocol suites.

The OSI reference model has seven layers:

  • Application layer (layer 7)
  • Presentation layer (layer 6)
  • Session layer (layer 5)
  • Transport layer (layer 4)
  • Network layer (layer 3)
  • Data Link layer (layer 2)
  • Physical layer (layer 1)

The OSI layers are divided into two groups. The top three layers define how the applications within ...

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