Is it possible to organize network time synchronization between network segments connected through a unidirectional gateway?

Question

linux

Good afternoon, colleagues!
There is approximately the following topology:
Internet -> open segment -> unidirectional gateway -> closed segment
Each segment has its own NTP server configured. Accordingly, in an open NTP segment, the server takes time from the Internet and distributes it to clients within the segment. In a closed segment, there is no access to an external server, so the time is manually set and distributed inside the segment. It often happens that the time between segments is out of sync by 5-10-15-20 minutes. Therefore, there is a problem of time synchronization between segments. I would like to use a unidirectional gateway for this.
The gateway is able to transmit data only from allowed IP addresses of the open segment via the UDP protocol. The transmission scheme is something like this:
Permitted IP (open segment) starts transmission to a special IP (open segment) specified in the gateway config
-------->
The gateway receives UDP packets and changes their header "Recipient Address" in accordance with the table specified in the config
- ------->
Sends a modified packet to a recipient in a private segment.
Is it possible to somehow organize synchronization in such a scheme? The option to purchase additional equipment is not yet considered)

Answer 1

In a closed network segment, you raise an ntp server, buy a GPS antenna and take time from it. I have such a scheme everywhere at work, gps antennas are all on rs232, ntpd is just a shaman and that's it. Everywhere it is about 40 objects, the accuracy of time is needed for the specificity of the software (telemetry of hardware and sensors).