I migrated this question from cryptography - as the acceptance or rejection of packages has usually little to do with cryptography.
Now I can imagine that it gets closed here, but the reason given is that it operates on a layer higher than OSI layer 4. According to any documentation I can find is that it operates (primarily) on the network layer (IP), which is OSI layer 3.
I explicitly looked at the help center and decided to migrate because I was pretty sure that it was not above layer 4 of the OSI model. So where did I reason incorrectly? Or is the mod giving the wrong reason?