OSI - Ref: OSI by Uyless Black, Prentice-Hall, 1991

• Presentation layer

  • Standardized encoding of data so that user applications can communicate with each other even though they might use different representations for their Protocol Data Units (PDU’s) {Remember those?}. Representations could be ASCII, Unicode etc.

• Application layer

  • What happens to the multitude of terminals with different escape sequences for inserting/deleting text etc? You create an abstract network virtual environment. Software maps the network virtual terminal to the physical terminal. Virtual terminal is in the application layer.
  • File Transfer: What to do when there are different file naming conventions, different ways of representing text lines etc. The file transfer application needs to handle such incompatibilities.

Reference Models/OSI layers

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