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.
The NIC operates on Layer 2 (Data Link Layer) of the OSI Model.
TELNET
Network layer
A NIC operates at those two layers.
application
- data Link
it may be network layer or transport layer.. it depends on the design of the firewall.. also depends on the requirement specification..
TCP operates at Layer 4 which is Transport of the OSI Model!
FTP operates in application layer of ISO OSI layered model.