[fanf2]

In my experience working alongside network engineers, they use “layer 2” as a synonym for Ethernet, “layer 3” as a synonym for IP (v4 and v6), “layer 4” as a synonym for TCP and UDP, and “layer 7” as a synonym for application protocols. They don’t talk about the other layers. It’s just jargon, without any deeper meaning.

[brookst]

Well yes, those are the network layers, so network engineers think about them the most.

Admittedly layers 5 and 6 are kind of blurry, but so what? Doesn’t mean the model isn’t useful, just that it isn’t a perfect map=territory.