5 ms·

I wonder, will the GPS jamming cause any disruption to (or, worse, deviation of) GPS time signals? If yes, that could cause some interesting effects to NTP ser

I wonder, will the GPS jamming cause any disruption to (or, worse, deviation of) GPS time signals? If yes, that could cause some interesting effects to NTP servers and appliances that use GPS as their stratum-zero source of time.

mlosapio 9y ago
SuperNAP is in that area. Only one of the largest colo’s in the country....no big deal
- itronitron 9y ago
  hopefully they have the necessary details from the USAF or have recently installed an atomic clock
jtolmar 9y ago
A few months ago one of the satellites was still broadcasting while it was down for routine maintenance, reporting some time that was off by a third of the distance to the sun. There are enough weird GPS errors that I'd hope they have a backup plan already.
- tjohns 9y ago
  Wouldn't the GPS ephemeris/almanac data would still list the satellite as inop, even if it's still transmitting?
  - jtolmar 9y ago
    They did, so actual GPS location chips weren't thrown off. But apparently there are GPS-based clocks out there that don't actually bother to read the almanac. (I'm a few layers removed from the error report where I saw this so I don't really know the details.)
itronitron 9y ago
if what they are doing is jamming, then if you are getting timing information from a gps receiver and your receiver is in range of the jammer you will get the timing information from the jamming signal, so yes, however the USAF _might_ be including the correct timing information in their jamming signal in order to reduce any side effects of their exercise...
- TeMPOraL 9y ago
  Isn't timing the primary signal you get from GPS? Including a correct time would defeat the point of jamming.
voxadam 9y ago
When a GPS disciplined time server or server appliance encounters a condition where the GPS signal becomes unavailable or unreliable a local oscillator is used to keep time. The local oscillator is generally a TCXO, OCXO, or Rubidium standard. Such systems are able to deliver fairly accurate and precise time in the event of a short outage like this. A quality server with a local Rubidium oscillator should be able to keep accurate time within 10 μsec in the event of a five day outage. GPS signals can become unavailable for numbers reasons that are far more mundane than being jammed such as someone disconnecting the antenna, lightning strike, a rat chewing through the cable, meth heads stealing the copper cable and/or antenna, etc.
api_or_ipa 9y ago
How many NTP servers run off GPS? My understanding was that most people just piggy backed off pool.ntp.org and didn't bother running their own stratum 1.
- michaelt 9y ago
  https://www.microsemi.com/product-directory/carrier-grade-ntp-ptp-grand-masters/4133-timeprovider-2700 https://www.microsemi.com/product-directory/carrier-grade-nt... Grandmaster Clock [...] equipment designed for deployment in the mobile backhaul network, at macro base station sites, or small cell aggregation locations. [...] meet the stringent timing and synchronization requirements of 4G/LTE networks In other words: Applications that need sub-millisecond-level precision, such as mobile phone base stations, where multiple towers coordinate their transmit/receive windows to avoid interfering with one another.
- gh02t 9y ago
  I'm currently building one for fun using a Raspberry Pi and a cheap GPS module from Aliexpress. I don't think a lot of hobbyists do it, but it's pretty common for stuff like datacenters to have their own local GPS disciplined NTP server. It's not that hard to make one yourself by the way, and the hardware costs about $15. At the pro level you can get rack mount units with GPS + an on board TXCO/OXCO/rubidium frequency reference. You can probably get one with a cesium reference too, but I don't think that's much use outside a metrology lab (and will cost a fortune). https://spectracom.com/products-services/precision-timing/enterprise-class-securesync https://spectracom.com/products-services/precision-timing/en... edit: if someone knows about how much these cost please comment, I'm curious but I don't want to request a quote. https://developers.redhat.com/blog/2017/02/22/how-to-build-a-stratum-1-ntp-server-using-a-raspberry-pi/ https://developers.redhat.com/blog/2017/02/22/how-to-build-a...
  - mtm 9y ago
    Interesting, I’m doing the same but using WWVB 60khz radio signal for my time source
    - 9y ago
pletnes 9y ago
They’ll be sending fake signals, i.e time shifted. Since the speed of light is enormous, we’re probably talking micro- to millisecond disturbances. No worries for regular NTP servers I’d imagine.

mlosapio 9y ago

SuperNAP is in that area. Only one of the largest colo’s in the country....no big deal

itronitron 9y ago
hopefully they have the necessary details from the USAF or have recently installed an atomic clock

jtolmar 9y ago

A few months ago one of the satellites was still broadcasting while it was down for routine maintenance, reporting some time that was off by a third of the distance to the sun. There are enough weird GPS errors that I'd hope they have a backup plan already.

tjohns 9y ago
Wouldn't the GPS ephemeris/almanac data would still list the satellite as inop, even if it's still transmitting?
- jtolmar 9y ago
  They did, so actual GPS location chips weren't thrown off. But apparently there are GPS-based clocks out there that don't actually bother to read the almanac. (I'm a few layers removed from the error report where I saw this so I don't really know the details.)

itronitron 9y ago

if what they are doing is jamming, then if you are getting timing information from a gps receiver and your receiver is in range of the jammer you will get the timing information from the jamming signal, so yes, however the USAF _might_ be including the correct timing information in their jamming signal in order to reduce any side effects of their exercise...

TeMPOraL 9y ago
Isn't timing the primary signal you get from GPS? Including a correct time would defeat the point of jamming.

voxadam 9y ago

When a GPS disciplined time server or server appliance encounters a condition where the GPS signal becomes unavailable or unreliable a local oscillator is used to keep time. The local oscillator is generally a TCXO, OCXO, or Rubidium standard. Such systems are able to deliver fairly accurate and precise time in the event of a short outage like this. A quality server with a local Rubidium oscillator should be able to keep accurate time within 10 μsec in the event of a five day outage. GPS signals can become unavailable for numbers reasons that are far more mundane than being jammed such as someone disconnecting the antenna, lightning strike, a rat chewing through the cable, meth heads stealing the copper cable and/or antenna, etc.

api_or_ipa 9y ago

How many NTP servers run off GPS? My understanding was that most people just piggy backed off pool.ntp.org and didn't bother running their own stratum 1.

michaelt 9y ago
https://www.microsemi.com/product-directory/carrier-grade-ntp-ptp-grand-masters/4133-timeprovider-2700 https://www.microsemi.com/product-directory/carrier-grade-nt... Grandmaster Clock [...] equipment designed for deployment in the mobile backhaul network, at macro base station sites, or small cell aggregation locations. [...] meet the stringent timing and synchronization requirements of 4G/LTE networks In other words: Applications that need sub-millisecond-level precision, such as mobile phone base stations, where multiple towers coordinate their transmit/receive windows to avoid interfering with one another.
gh02t 9y ago
I'm currently building one for fun using a Raspberry Pi and a cheap GPS module from Aliexpress. I don't think a lot of hobbyists do it, but it's pretty common for stuff like datacenters to have their own local GPS disciplined NTP server. It's not that hard to make one yourself by the way, and the hardware costs about $15. At the pro level you can get rack mount units with GPS + an on board TXCO/OXCO/rubidium frequency reference. You can probably get one with a cesium reference too, but I don't think that's much use outside a metrology lab (and will cost a fortune). https://spectracom.com/products-services/precision-timing/enterprise-class-securesync https://spectracom.com/products-services/precision-timing/en... edit: if someone knows about how much these cost please comment, I'm curious but I don't want to request a quote. https://developers.redhat.com/blog/2017/02/22/how-to-build-a-stratum-1-ntp-server-using-a-raspberry-pi/ https://developers.redhat.com/blog/2017/02/22/how-to-build-a...
- mtm 9y ago
  Interesting, I’m doing the same but using WWVB 60khz radio signal for my time source
  - 9y ago

pletnes 9y ago

They’ll be sending fake signals, i.e time shifted. Since the speed of light is enormous, we’re probably talking micro- to millisecond disturbances. No worries for regular NTP servers I’d imagine.