Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd)

[stephenw10]

I have found it surprising how well GPS works with a restricted view of the sky. Of course when you look into GPS it's amazing it works at all.

[RobbieTT]

@Sergei_Shablovsky said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

Maximum shielded wire connection to GPS satellite (!!!, no GSM-source from cellular base station nearby!) antenna to small electrical scheme and than for motherboard’s DB-9 of RS-232 MUST BE LESS than ~15m.

This also mean that You need place the GPS satellite antenna to rooftop where are 180 degrees on both X and Y axes of clear sky view to receive signals from no less than 3 satellite. And no any skyscrapers nearby, no any big trees or hi-powered (3-5-20kWA electrical lines) on a distance 50-200m.

So, back to the server room, as a result You have only 2-3m of this shielded wire from hole in the wall to DB-9 of RS-232 in server.

But anyway, it’s not “just put the GPS antenna somewhere out of the server room”. Definitely not.

I scratching my head a little at what you are aiming at but little of what you say here is true. I can help to resolve these errors though.

You don't need an antenna from a roof to a server; indeed, in many situations this would be a bad idea. GPS time source equipment can be colocated with, close to or even combined with the antenna. This time source can then be distributed by the network cabling - it is a network time after all.

You don't need 180º X & Y view of a clear sky - far from it. With that kind of view you would, at times, exceed 12 satellites. Additionally, GPS orbits are far from geostationary. The rip around our planet pretty quickly in predictable patterns for the GPS almanac to form a dynamic lattice that, from a receiver's perspective, will provide suitable sources with only a limited amount of LoS available. It is a far cry from where we started, when we had a limited constellation and warfare cognisant of GPS-dawn and sunset.

Regarding satellites needed, for a meaningful position you really need 4 satellites, dropping to 3 if a known or predictable height is available. But yes, if you are driving your server room and roof around Manhattan then having more satellites available would help. If your building is more known for being immovable and even surveyed as such then you only need a view of 1 GPS satellite at a time to use GPS timing.

Of course, GPS is not for everyone and even it it was the usual redundancy and diversity considerations would see it augmented by dedicated fibre, ToD receivers, GSM, ToD beacons plus atomic clocks et al. Whilst my experience is more at the strategic scale of GPS management I do have a Veracity Timenet GPS unit on my home network. My network rack is surrounded by concrete and below any achievable LoS and I would never run an external antenna directly to it.

I do have an external pole-mount antenna in a box but waiting for the next round of roof work to fit it. I'm in no hurry as the network GPS receiver has a simple patch antenna on an upstairs window with a short cable to the receiver, which is plugged into the nearby ethernet socket. Even In this 'terrible' location it has at least 8 satellites to work with.

Not everything is difficult.

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[RobbieTT]

This is how craptostic a timing reference can be located - at the rarely photographed arse-end of my network. The blue arrows are the GPS/PPS network timing box, stuck on the backside of a bedroom TV and the patch antenna sitting on a window sill:

The secret to comedy.

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[johnpoz]

@RobbieTT yeah I use to have the antenna just sitting on the top of my desk in my office and would work.. I did move it to the garage a while back and the antenna sits on top of the garage door railing.. Can see more sats from there. I believe my problems in the office started after we added way more insulation in the attic.. There is no insulation above it where its at in the garage.

The pi sits behind my TV in living room, where the cable runs through the wall into the garage..

I am not a guru when it comes to the stuff, but it is fascinating to me. From my understanding the time from the sats to be accurate you need to work out some math and set a fudge, etc. to account for stuff. I was just more after the pps signal the gpshat provides once it can see enough sats.. I never bothered to work out the correct fudge factor

While I might be off by a few ms of "true" time.. It was a fun project to setup, and for sure is close enough for me.. My little pi ntp server also polls just ntp servers out on the internet. From the output of ntpq the gps time on shm (0) is not even a candidate, if the pps source would go away.

Which was my problem I was seeing, couldn't see enough sats to get sync I believe and so pps was never kicking in. Once I moved the antenna to the garage that started working again.. From the output of cgps shows I can see a lot of sats.

But it for sure worked before just with the antenna in my office.. Not even near a window, etc.

I think the total cost, with the pi was under a hundred bucks total.. The pi, the hat, the little antenna, everything. And I already had the pi so cost of the project was just the hat, the antenna to be honest.. ntp and talking to sats is for sure a fun little project, if this sort of stuff interests you.. And can be done for very reasonable "hobby" money if you will.

Is my little ntp server providing "true" time that you would need in some scientific setting - prob not.. But it very stable, ie it doesn't drift much and I like having it running it on my network and syncing all my devices too it.. Even if its off by a few ms from "true"..

[stephenw10]

@RobbieTT said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

The secret to comedy.

Ha

[JKnott]

@Sergei_Shablovsky said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

But anyway, it’s not “just put the GPS antenna somewhere out of the server room”. Definitely not.

You put the receiver and NTP server elsewhere, where there is a signal. Nothing new here. Often, both devices are in the same box. Here is one example.

[JKnott]

@RobbieTT said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

GSM

GSM is dying, if not already dead in most areas. These days, a 4G or 5G network can provide 1.5 µS accuracy. It will likely work better than GPS in many locations.

[RobbieTT]

@JKnott said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

@RobbieTT said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

GSM

GSM is dying, if not already dead in most areas. These days, a 4G or 5G network can provide 1.5 µS accuracy. It will likely work better than GPS in many locations.

Not sure why you picked-out GSM time reference from the list but the world is a big place and GSM-based time reference systems are out there in use for everything from military, police, ATC, banking, PoS, trading, networking, power networks, gas network, train signal & monitoring... and the list goes on.

I happen to live on a bit of the planet that is more advanced than other areas and we have a desire is to cease GSM use by 2033 (IIRC) but given that there are still major infrastructure elements that are not on track to meet that deadline some slippage will probably occur.

Again, we are talking timing reference use, not using a phone to call your kids. Most of the population of any given country does not have a clue about RF spectrum management let alone any idea* as to what uses or depends on GSM.

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[* Ok, this bit varies by country. Here in the UK there is growing public awareness that the typical domestic gas and electric meter will become 'dumb' soon and that medical service providers for home equipment (dialysis, CPAP, respirators etc) have quite a problem. But the average punter has no idea about substations, sewage, hydroelectrics or indeed all the other infra held together on obsolescent tech.]

[JKnott]

@RobbieTT

In many areas, GSM is gone. On my carrier, it's already been reduced to 1 band from 2. Also, spectrum costs the cell companies a lot of money. Do you think they're going to leave some spectrum they already have to sit almost unused and then spend on more spectrum? Already we're hearing about things like security systems and more not working because 2G & 3G are being discontinued. The world moves on and sticking with obsolete tech is not the way to go, even if there still is some GSM in your area. A few years ago, a friend received a free 4G phone because the company he was with was in the process of shutting down 2G & 3G.

So, hang onto your GPS time source for as long as you can, but don't be surprised if it stops working some day.

Another source which you didn't mention was NTSC TV signals. Some stations transmitted the time during the horizontal blanking interval and the colour burst oscillator was an excellent stable signal. Are those stations supposed to keep broadcasting, even though NTSC is rarely used these days?

[dennypage]

@JKnott said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

Here is one example.

TM1000A. I have one of those in a box somewhere as well, along with a TM2000A. The TM1000A NTP implementation was written in microcode, and was one of the very few to have implemented the broadcast mode of NTP. The TM2000A was focused on PTP, which it was reasonably good at, but instead of a microcode implementation for NTP it used busybox which made it a very poor NTP server.

[RobbieTT]

@JKnott said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

@RobbieTT

Do you think they're going to leave some spectrum they already have to sit almost unused and then spend on more spectrum? The world moves on and sticking with obsolete tech is not the way to go, even if there still is some GSM in your area.

Whilst I was a member of the UK Frequency Allocation Committee we did cooperate with other national and international bodies (FCC, WRC etc) - otherwise how would we know, for example, that Tajikistan (amongst others) uses 25 kHz for time signals. It's been a few years since I left that role but the RF spectrum remains stubbornly fixed.

Again, please don't confuse the GSM you used to use for phone calls with the use of GSM time references or other industrial uses.

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[JKnott]

@RobbieTT

There are a lot of time signals, on a variety of frequencies, around the world. They are broadcast stations and not likely to go away. Is there some other GSM out there, beyond the cell phone network? Also, CDMA was the 2G tech used for accurate time keeping, not GSM, which uses TDMA.

If it is the GSM cell network you're referring to then yeah, it's going away in the not too distant future. My friend's phone that had to be replaced was 2G CDMA.

BTW, I have a clock that's supposed to set itself with the 60 KHz WWVB signal. However, it hasn't worked in years and didn't very well when it did. I have also used WWV as a frequency standard and it & CHU for time of day. As I said, lots of time signals around the world.

[Sergei_Shablovsky]

@johnpoz said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

@sergei_shablovsky said in Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

You have separate machine especially for timeserver?

Yeah I have a raspberry pi with a gps hat that I use as my networks stratum 1 server, and also serve this up to the ntp pool via both ipv4 and IPv6 ;)

BTW, why You have so much distortion in offsets? (Probably Pi not sufficient horsepower to keep many requests? What is loading of CPU/RAM/SSD?)

This is our recent

[NollipfSense]

@RobbieTT said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

Dedicated NTP time sources don't have to be expensive or be a hacky DIY job on a RPi.

I am watching this reasonable priced one on eBay: https://www.ebay.com/itm/385524217975

[dennypage]

@NollipfSense Haven't tested one of those myself, but more information can be found here: https://fc-ntp-100.toimii.fi.

FWIW, at 0.5-2ms the advertised accuracy for NTP on the LAN is low. This implies a simplistic NTP implementation without hardware timesamping.

For around the same price, you could do a Pi.

[NollipfSense]

@dennypage said in Chrony, PTP, Network Time Security (NTS, NTPsec) to replace unsecure/old NTP (ntpd):

here: https://fc-ntp-100.toimii.fi.

Cool...thank you for sharing.