Gateway clarification - layer of operation
Just a simple question to clarify the layer at which Gateways operate at. Various resources have different answers. In the AIO book they say that Gateways operate at the Layer 7 (Application Layer), in the CBT nuggets video tutorials they say Gateways operate at the same level as Routers, layer 3(Network Layer). After the 2 different answers i did a search on Google and found yet again different answers, many resources say Gateways operate at all the Layers of the OSI model. What is the correct layer for the basic operation of Gateways as it pertains to the CISSP exam? So if the question was " at what layer of the OSI model do gateways operate?" and the available answer were the 7 layers of the OSI model, which layer would be the correct one.