Reliable and guaranteed one-way time distribution is important in complex systems where multiple air-gapped security domains need to have a common system time. This can easily be realized using the solution shown below where time (NTP protocol) is distributed from a common NTP Server over diodes to the different Security Domains using Diode:NTP.
In each Security Domain the receiving proxy can act as NTP Server for all clients in the domain. If is also possible to add an additional NTP Server in each Security Domain. If the receiving proxy acts as NTP Server it is recommended to use a physical proxy.