So they put a rubidium oscillator in the Cisco boxes or upgraded their current equipment line. slide 15 has other solutions to gps denial. https://www.gps.gov

So they put a rubidium oscillator in the Cisco boxes or upgraded their current equipment line. slide 15 has other solutions to gps denial. https://www.gps.gov/cgsic/meetings/2016/silverstein.pdf https://www.gps.gov/cgsic/meetings/2016/silverstein.pdf IEEE 1588-2008 is a good solution at 10 updates per second.