Stateful packet inspection
Application gateway/proxy
generally layer 4, but SOCKS operates at layer 5, which allows it to work well with applications
It operates on the data link layer of the OSI model (level 2). The switch creates a separate collision domain for each port. Although some switches operate on level 3 of the model and are called multi-layer switches.
TELNET
The NIC operates on Layer 2 (Data Link Layer) of the OSI Model.
A NIC operates at those two layers.
Network layer
application
- data Link
FTP operates in application layer of ISO OSI layered model.
If you mean the MAC address, that's a layer-2 concept.
TCP operates at Layer 4 which is Transport of the OSI Model!