give proper solution for both (A) and (B) give proper explaination subject networking (a) The purpose of the OSI model is to show how to facilitate communication between different systems without...

give proper solution for both (A) and (B) give proper explaination  subject networking

(a)

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  The purpose of the OSI model is to show how to facilitate communication between different systems without requiring changes to the logic of the underlying hardware and software? In contrast to TCP/IP model this model is not practically implemented and TCP is practical. Why? Answer with valid reasons.
  

(b)

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  Nowadays, the “store-and-forward network” technique is not using in general communications, why? Also describe it’s working.