Which layer of the OSI model does the application gateway examine?

The application gateway primarily operates at the session (Layer 5) and application (Layer 7) layers of the OSI model. This function allows it to effectively manage and monitor the communication between different applications, as well as facilitate the control of data transmission while ensuring security measures are in place.

At Layer 5, the application gateway can establish sessions between communicating systems, maintaining stateful connections and managing session attributes. This functionality is essential in environments where secure communication is critical.

At Layer 7, the application layer, the gateway directly interacts with application-level data, enabling it to scrutinize, filter, and even translate content as needed. This can involve interpreting specific application protocols and can be vital for tasks like web filtering, proxy services, or ensuring compliance with security policies.

Other layers in the OSI model do not provide the same level of access to application data or the capabilities for managing secure sessions. Thus, the focus of the application gateway on Layers 5 and 7 allows for a comprehensive approach to application-level communication, making it effective in various security and networking scenarios.