Every explanation about the OSI Model (or other Models) always gives me the impression that the data (PDU) from the top layer (Application Layer, L7) always go through all of the layers until the bottom layer (Physical Layer, L1).
Does the PDU always go through all the 7 layers in the OSI Model? Or we can choose until which layer we want to apply our communication protocol?
These examples might explain more about my confusion.
Let's say I have an IPSec (Network Layer, L3) hardware on an FPGA. IPSec provides many Security Services already. Does it mean I bypass the Datalink Layer?
Another example is when we are communicating via SSL. Does it mean I bypass all the layers after it except the Physical Layer?