Relatively speaking, firewalls operated at the physical level of the seven-layer OSI model are:
almost always less efficient.
almost always less effective.
almost always less secure.
almost always less costly to setup.
None of the choices.
Early attempts at producing firewalls operated at the application level of the seven-layer OSI model
but this required too much CPU processing power. Packet filters operate at the network layer and
function more efficiently because they only look at the header part of a packet. NO FIREWALL
operates at the physical level.