Domain 2, “Network Security and Telecommunications”

ISO/OSI Seven-Layer Model

The ISO/OSI seven-layer model defines the fundamental aspects of how all network communication occurs. The OSI model exists to enable the user to understand the totality of a very complex system of communications by breaking the overall transmission of data into seven easier-to-define layers:

  • Application layer— Primarily responsible for interfacing with the user. This is the application interface the user experiences. (POP3, NNTP)

  • Presentation layer— Primarily responsible for translating the data from something the user expects to something the network expects. (WAV, MIDI, JPEG, SMB)

  • Session layer— Primarily responsible for dialog control between systems and applications. ...

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