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.

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Comments

tchoki

Gateways operate at the presentation layer per ISC2 . That layer does translation which is a function of gateways.

philz1982

Need to define gateway. Protocol gateway, or data plane gateway? Protocol gateways span layer 4-7. Data plane gateways span layers 2-3.

JDMurray

"Gateway" is a very ambiguous term that generally means a transit point between two different networks where some sort of transformation (translation) or decision making process takes place. Presentation layer gateways convert data from one format to another (e.g., ASCII/EBCDIC, binary/base64, raw bitmap/PNG, compression, encryption) for compatibility with different applications, OSes, or networks. Firewalls are sometimes called "security gateways" because they form the borders of zones with differing levels of security. A NAT router (or firewall) is as type of routing information translation gateway. Application gateways handle translation and control (proxy) of the information flow between specific applications, such as HTTP/S between a Web client and Web server.

So you see that a gateway can really be implemented at any OSI layer, but I think layers 5 (for data transformation) & 7 (for protocol translation and control) are where the CISSP will say gateways reside.