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Upper OSI Layers

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Session layer, Presentation Layer

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Upper OSI Layers

  1. 1. Upper OSI Layers DESEAR, HYACINTH GALINO, JENNY
  2. 2. Session Layer
  3. 3. Responsibilities of the session layer  Dialog control  Synchronization  Activity management  Exception handling
  4. 4. Dialog Control  COMMUNICATION BETWEEN TWO PROCESSES  DECIDES WHOSE TURN IT IS TO TALK  IMPLEMENTED THROUGH THE USE OF A DATA TOKEN
  5. 5. Dialog Control
  6. 6. Synchronization  ALLOWS A PROCESS TO ADD CHECKPOINTS TO A STREAM OF DATA  ACHIEVED THROUGH THE USE OF SEQUENCE NUMBERS  MAJOR AND MINOR SYNCHRONIZATION POINTS
  7. 7. Synchronization
  8. 8. Activity Management  IDENTIFIES WHERE DATA STARTS AND ENDS  DIVIDES DATA STREAM INTO ACTIVITIES
  9. 9. Exception Handling  A GENERAL PURPOSE MECHANISM FOR REPORTING ERRORS
  10. 10. Session-layer protocols  Point-to-Point Tunneling Protocol (PPTP)  Remote Procedure Call Protocol (RPC)  Real-time Transport Control Protocol (RTCP)
  11. 11. Presentation Layer
  12. 12. Responsibilities of the presentation layer  Translation  Encryption  Compression
  13. 13. Translation  INFORMATION IS CHANGED TO BIT STREAMS BEFORE IT IS TRANSMITTED.  RESPONSIBLE FOR INTEROPERABILITY BETWEEN DIFFERENT ENCODING METHODS.  MUST BE ABLE TO TRANSLATE BETWEEN MULTIPLE FORMATS BY USING A COMMON FORMAT
  14. 14. Common translation formats  ASCII  Binary  EBCDIC sample: ASCII to binary
  15. 15. Encryption  TO ENSURE PRIVACY OF SENSITIVE INFORMATION  TRANSFORMS ORIGINAL INFORMATION TO OTHER FORM BEFORE SENDING IT OUT OVER THE NETWORK. ACHIEVED BY CRYPTOGRAPHY  DECRYPTION IS THE REVERSE OF ENCRYPTION IT TRANSFORMS THE DECRYPTED INFORMATION TO ITS ORIGINAL READABLE FORM
  16. 16. Sample forms of cryptography  Microdots  Merging words with images  Ciphertext
  17. 17. Compression  REPRESENT AN INFORMATION SOURCE AS ACCURATELY AS POSSIBLE USING THE FEWEST NUMBER OF BITS  COMPRESSING DATA REDUCED STORAGE AND/OR COMMUNICATION COSTS  IMPORTANT IN AREAS OF DATA TRANSMISSION AND DATA STORAGE SUCH AS TEXT, AUDIO AND VIDEO
  18. 18. Why compression is important  Reduced size of file to half is equivalent to doubling the capacity of the storage medium  It becomes feasible to store data at a higher, thus faster, level of the storage hierarchy.
  19. 19. Why compression is important  It reduce the load on the input/output channels of the computer system
  20. 20. Presentation Layer Protocols  Apple Filing Protocol (AFP)  External Data Representation (XDR)  X.25
  21. 21. That’s all folks!

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