Basic principles of the OSI model
OSI-model is based on the concept of peer-to-peer communications, where two layer (N) protocol entities communicate using a (N) protocol
Layer (N) is based on the service provided by layer (N-1), it adds value to the (N-1) service and provides more refined (N) service to layer (N+1)
The layers are independent and only ”see” each other through the service interfaces between the layers
(N+1) entity uses (N) service through (N) service primitives
(N) entity communicates with its peer entity by exchanging (N) Protocol Data Units (or (N) PDUs)