Which of the following exists between the client and the server system to provide security and allows customized NAT traversal filters to be plugged into the gateway to support address and port…

An Application-level gateway operates at the application layer between client and server, inspecting and rewriting payload content to support NAT traversal for protocols like SIP, FTP, and H.323 that embed IP addresses in their data. It supports pluggable filters that can be added to the gateway to handle the specific address and port translation logic each protocol requires, which a standard stateful firewall or NAT device cannot accomplish on its own.

A proxy server forwards client requests on behalf of clients but does not provide pluggable, protocol-specific NAT traversal filters for application-layer address translation.

A firewall enforces access control rules and can perform stateful inspection but does not natively support pluggable application-layer NAT traversal filters for modifying payload-embedded addresses.

A DMZ is a network architecture segment that isolates public-facing servers from internal networks; it is not a device that performs application-layer NAT traversal or protocol filtering.