<P> A unidirectional network (also referred to as a unidirectional security gateway or data diode) is a network appliance or device allowing data to travel only in one direction, used in guaranteeing information security . They are most commonly found in high security environments such as defense, where they serve as connections between two or more networks of differing security classifications - also known as a "cross domain solution ." This technology is also found at the industrial control level for such facilities as nuclear power plants, electric power generation / distribution, oil and gas production, water / wastewater, airplanes (between flight control units and in - flight entertainment systems), and manufacturing . </P> <P> The physical nature of unidirectional networks only allows data to pass from one side of a network connection to another, and not the other way around . This can be from the "low side" or untrusted network, to the "high side" or trusted network, or vice versa . In the first case, data in the high side network is kept confidential and users retain access to data from the low side . Such functionality can be attractive if sensitive data is stored on a network which requires connectivity with the Internet: the high side can receive Internet data from the low side, but no data on the high side are accessible to Internet - based intrusion . In the second case, a safety - critical physical system can be made accessible for online monitoring, yet be insulated from all Internet - based attacks that might seek to cause physical damage . In both cases, the connection remains unidirectional even if both the low and the high network are compromised, as the security guarantees are physical in nature . </P>

What is the name given to a one way data transmission