Unidirectional network

A unidirectional network (also referred to as a unidirectional gateway or data diode) is a network appliance or device that allows data to travel in only one direction. Data diodes can be found most commonly in high security environments, such as defense, where they serve as connections between two or more networks of differing security classifications. Given the rise of industrial IoT and digitization, this technology can now be found at the industrial control level for such facilities as nuclear power plants, power generation and safety critical systems like railway networks.

Initially, data diodes were only a network appliance or device allowing raw data to travel only in one direction, and were used in guaranteeing information security or protection of critical digital systems, such as industrial control systems, from inbound cyber attacks. After years of development, they evolved towards combinations of hardware and software running in proxy computers in the source and destination networks, with the hardware enforcing physical unidirectionality and the software replicating databases and emulating protocol servers to handle bi-directional communication. Data diodes are now capable of transferring multiple protocols and data types simultaneously.

Data diodes are commonly found in high security military and government environments, and are now becoming more widespread in sectors like oil & gas, water and wastewater, airplanes (between flight control units and in-flight entertainment systems), manufacturing and cloud connectivity for industrial IoT. New regulations have increased demand and with increased capacity, major technology vendors have lowered the cost of the core technology.