In this context, a frame is typically an entity at the physical layer.
They only travel through solid material, and so are stopped at the liquid layer in the Earth's core.
At the physical layer, hubs support little in the way of sophisticated networking.
She leaned down to take a closer look at the layer of dirt.
And she could easily stop at the first layer if she wanted to.
In seconds they were at the outer layer of the atmosphere.
This address is needed at the layer below the push access protocol.
I don't think that was even thought about at the layer you are working on.
Windows actions which act on disks at the physical layer are not possible.
While the army has some three million troops, the only ones whose loyalty the leaders worry about are those at the top layer or two.