Which of the following devices typically works at the Application layer and acts as a protocol translator for different environments?

A.
Switch

B.
Gateway

C.
Bridge

D.
Hub

Explanation:
Software gateways are more complex devices than the other mentioned
devices because they look within the frame to gain more than just address and
routing information. Translation may need to be performed when entities on two
unlike environments need to communicate, as in a Novell and Microsoft network using
proprietary protocols. (Although gateways can work at different OSI layers, the
CISSP exam usually puts them at the Application layer.)