This is a potential security issue, you are being redirected to https://csrc.nist.gov
A device with appropriate mechanisms that: (i) facilitates the adjudication of different interconnected system security policies (e.g., controlling the flow of information into or out of an interconnected system); and/or (ii) provides information system boundary protection.
CNSSI 4009-2015 NIST SP 800-53 Rev. 4
NIST SP 800-53 Rev. 4 under Boundary Protection Device