What are the two principles of Protocol Layering use your ow

What are the two principles of Protocol Layering? (use your own words to answer question)

Solution

Following are the 2 principles of Protocol Layering :

1) First Principle : Each layer should perform 2 opposite tasks, one in each direction.
eg. the second layer of OSI model (Session layer) can both encrypt and decrypt.

2) Second Principle : The 2 objects under each layer at both sites (sender and receiver) should be identical.
eg. Objects at both sites (sender and receiver) of layer 2 in OSI model should be a ciphertext letter.

Similarly,  Objects at both sites (sender and receiver) of layer 1 in OSI model should be a mail format.