Score is low and not raising

[ProGeek]

Hello,
i have 2 IPv6 servers made publicly some days ago.
Servers are build around Raspberry PI and U-blox GPS modules, using PPS and GPIO.
The problem is that i try to make the servers available in pool, but i get constant -20 on rating.

Any idea how can i improve the score?

https://www.ntppool.org/scores/2a02:2f04:a0e:9199:99::2

https://www.ntppool.org/scores/2a02:2f04:a0e:9199:99::2

[William Unruh]

You give no details at all so it is hard to figure out what you are
doing never mind what is wrong. It seems you have a 500 ms (1/2 second)
offset, which really is pretty terrible. Wrong edge on the interrupt?
( and at the end it inexplicably drops to 100ms, which is still pretty
terrible but better-- what changed)

Hook you Pis up to the network, and compare your PPS yourself to some
pool server. That way you can debug yourself instead of others doing it
for you.

[ProGeek]

hello,

I am using Chrony as a server.

i manage to lower the offset to 97ms hope is OK like this...or i will try new settings

now chrony stats reports are like this:

MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#* GPS0 0 3 377 5 -1167us[-2018us] +/- 98ms
#x PPM1 0 3 377 4 -406ms[ -406ms] +/- 2497us
#? PPS0 0 3 0 - +0ns[ +0ns] +/- 0ns

[William Unruh]

On 2021-06-08, ProGeek <prog...@gmail.com> wrote:
> hello,
>
> I am using Chrony as a server.
>
> i manage to lower the offset to 97ms hope is OK like this...or i will try new settings
>
> now chrony stats reports are like this:
>
> MS Name/IP address Stratum Poll Reach LastRx Last sample
>===============================================================================
> #* GPS0 0 3 377 5 -1167us[-2018us] +/- 98ms
> #x PPM1 0 3 377 4 -406ms[ -406ms] +/- 2497us
> #? PPS0 0 3 0 - +0ns[ +0ns] +/- 0ns

Well, pps is not working at all. I have no idea what PPM1 is, and your
system is using GPS0 as its source, which is not a good idea, since it
will be out by many may ms. If you got pps to work, it should have an
accuracy or a few micro seconds, not many ms. (GPS is the NMEA sentences
which are always delayed by about over 100ms.)

So, figure out why pps is not working, and fix that. In the meantime
without your system actually set up properly in itself, you should not
be going onto the pool and leading others astray.

[ProGeek]

ok,
fixed.

now stats looks like this:


Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================
GPS0 6 3 82 +16.101 190.363 -80ms 1527us
SHM1 7 4 94 +0.000 0.020 -740ms 239ns
PPS0 7 4 94 +0.000 0.020 +0ns 239ns

MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================

#? GPS0 0 4 377 10 -80ms[ -80ms] +/- 100ms
#- SHM1 0 4 377 11 -740ms[ -740ms] +/- 1000us
#* PPS0 0 4 377 11 +264ns[ +922ns] +/- 208ns

Hope that will make the score higher

[William Unruh]

As I said, at a minimum run a test in which you have at least one
network pool source to compare your system with some independent outside
system. Why demand that pool people do it for you? Since you want to be
on the pool you must have network connectivity.

[Roger]

On Tue, 8 Jun 2021 08:30:31 -0700 (PDT), ProGeek
<prog...@gmail.com> wrote:

>Hope that will make the score higher

Excuse me for my rudeness but forget the bloody scores. You need
to concentrate on having low offsets for months at a time. Look
at these two servers which are both using GPS.

https://www.pool.ntp.org/scores/212.159.133.83
https://www.pool.ntp.org/scores/185.57.191.229

Look at the left hand axes; 16 to -4 ms for the first, 0.2 to
-0.6 ms for the second. Your graphs range from 2 to -2 seconds.
Both servers are currently showing an offset of 500 ms. Useless
to the pool at present. Once your offsets are good the scores
will automatically be good.
--
Roger

[William Unruh]

Actually for GPS discipline, the offsets should be much better than 1ms.
It should be more like 1us, ie 1000 times better. Of course much of the
trouble could be due to connection problems between the machine and
Newark NJ which is trying to measure the offset (but even then 1ms seems
like a lot).

[chris]

On 06/08/21 20:42, Andreas Mattheiss wrote:
> Hello,
>
> just as additional source of information: I have a similar setup here
> (ublox PPS into a proper serial port of a PC) and I see a stable offset of
> -3 ms to 3 servers on the net (-3 ms to any of them). I'm using ntpd
> though.
>
> Regards
> Andreas
>
This is what I see at the ntp host here:

chris@ntp-host:~ % ntpq -pn
remote refid st t when poll reach delay offset jitter
======================================================================
o127.127.22.0 .PPS. 0 l 1 8 377 0.000 0.000 0.001
+192.9.200.168 .GPS. 1 u 10 64 377 0.193 0.001 0.054
*192.9.200.169 .GPS. 1 u 7 64 377 0.354 0.008 0.046

Using mini pc host with two network interfaces, internet and internal
network facing. FreeBSD 12 with ttl pps into the serial port dcd line
via a ttl to rs232 converter...

Chris

[ProGeek]

this is what i see on sourcestats:

210 Number of sources = 7
.- Number of sample points in measurement set.
/ .- Number of residual runs with same sign.
| / .- Length of measurement set (time).
| | / .- Est. clock freq error (ppm).
| | | / .- Est. error in freq.
| | | | / .- Est. offset.
| | | | | | On the -.
| | | | | | samples. \

| | | | | | |
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================

GPS0 12 6 176 -29.089 42.914 -8857us 1790us
SHM1 12 7 178 +0.000 0.010 -530ms 435ns
PPS0 12 7 178 +0.001 0.011 +3ns 445ns
blackmamba-g0.eff.ro 2 0 77 -0.005 2000.000 +501ms 4000ms
188.213.49.35 9 6 184 -0.748 21.608 +492ms 721us
time.cloudflare.com 6 4 81 +1.162 9.574 +500ms 72us
time.cloudflare.com 14 11 168 +0.502 0.939 +500ms 42us

if i get the results from PPS0 the offset is low, but is still reported high. and also correspond with the external time servers.

my settings are like this:

# SHM(0), gpsd: NMEA data from shared memory provided by gpsd
refclock SHM 0 refid GPS0 poll 4 precision 1e-1 trust noselect offset 0.646

# SHM(1), gpsd: PPS0 data from shared memory provided by gpsd
refclock SHM 1 refid SHM1 poll 4 precision 1e-3 lock GPS0 trust noselect offset 0.5300

# PPS: /dev/pps0: Kernel-mode PPS ref-clock for the precise seconds
refclock PPS /dev/pps0 refid PPS0 poll 4 precision 1e-7 lock GPS0 trust prefer delay 0.50

something is off but i can't pinpoint what

[chris]

Just using a standard ntpd here, as it's more than adequate for the
task, with minimum granularity in microseconds. Does look like there
is something seriously wrong, as the gps is 8mS out, and should be
fractions of a mS if working right.

What I would try is to strip out all except the pps and gps sources
and see what the offset looks like. Also, please post the ntpd.conf
file, as that can skew everything if misconfigured. Finally, check
the polarity of the pps signal, as the ~500mS offset for several
sources, (0.5 x 1sec), suggest pps input needs an inversion, but the
ntp.conf file has a line to define that...

[William Unruh]

Sorry but that is nuts.
Your external sources are 500ms ( 1/2 sec) off from the internal ones.
But that is probably because you told your system to screw up the
internal sources.

>
> my settings are like this:
>
> # SHM(0), gpsd: NMEA data from shared memory provided by gpsd
> refclock SHM 0 refid GPS0 poll 4 precision 1e-1 trust noselect offset 0.646

Why that offset? and why precision of 1e-1?

>
> # SHM(1), gpsd: PPS0 data from shared memory provided by gpsd
> refclock SHM 1 refid SHM1 poll 4 precision 1e-3 lock GPS0 trust noselect offset 0.5300

Why that offset?
Also, why are you having both gpsd and pps0 delivering data? It is the
same pps. And they fight each other-- when one interrupt is processing,
the other one is locked out. This makes the accuracy of pps less than
it should be (by a factor of about 10)
Tell gpsd not to use the PPS.

>
> # PPS: /dev/pps0: Kernel-mode PPS ref-clock for the precise seconds
> refclock PPS /dev/pps0 refid PPS0 poll 4 precision 1e-7 lock GPS0 trust prefer delay 0.50

Why that delay?

HOw about getting rid of all of the offset and delay stuff on your
internal sources.

>
> something is off but i can't pinpoint what

Sure is.

[William Unruh]

No, it should not be. GPS is the NMEA sentences from the gps device. It
is usually delayed by from .1 to .3 sec. Ie, it keeps terrible time.
It is the PPS that is spot on to the ns level.

>
> What I would try is to strip out all except the pps and gps sources
> and see what the offset looks like. Also, please post the ntpd.conf

He did post the sentences from the chrony.conf file ( the equivalent to
the ntpd.conf file) and they are weird.

> file, as that can skew everything if misconfigured. Finally, check
> the polarity of the pps signal, as the ~500mS offset for several
> sources, (0.5 x 1sec), suggest pps input needs an inversion, but the
> ntp.conf file has a line to define that...

It may be that he has chosen the wrong polarity, but I suspect he has
simply chosen the wrong options (the delay and offset options).


>

[chris]

Well, we know that, but if there is an available PPS, that becomes
the primary reference for the local system.

>>
>> What I would try is to strip out all except the pps and gps sources
>> and see what the offset looks like. Also, please post the ntpd.conf
>
> He did post the sentences from the chrony.conf file ( the equivalent to
> the ntpd.conf file) and they are weird.

Not familar with chrony, but why not go back to basics, run a stock
ntpd, which works out of the box. Why make life difficult, when ntpd has
more than adequate precision for the task ?. Experiment with other
solutions once the basics are known working and experience gained.

>
>> file, as that can skew everything if misconfigured. Finally, check
>> the polarity of the pps signal, as the ~500mS offset for several
>> sources, (0.5 x 1sec), suggest pps input needs an inversion, but the
>> ntp.conf file has a line to define that...
>
> It may be that he has chosen the wrong polarity, but I suspect he has
> simply chosen the wrong options (the delay and offset options).
>

If the 1pps signal has a 50% m/s ratio, then the ~0.5second offset on
the external sources is a glaring indicator of wrong polarity...

[William Unruh]

On 2021-06-10, chris <chris-...@tridac.net> wrote:
>
> Not familar with chrony, but why not go back to basics, run a stock
> ntpd, which works out of the box. Why make life difficult, when ntpd has
> more than adequate precision for the task ?. Experiment with other
> solutions once the basics are known working and experience gained.

chrony IS the basics, just as ntpd is. I believe he is piling on
options, when he should just try things straightforardly. At present, he
is telling chrony to offset the GPS and the SHM ( which is another pps,
which interferes with the kernel pps) by 1/2 sec, and discovers that
things are out by 1/2 sec.

>
>>
>>> file, as that can skew everything if misconfigured. Finally, check
>>> the polarity of the pps signal, as the ~500mS offset for several
>>> sources, (0.5 x 1sec), suggest pps input needs an inversion, but the
>>> ntp.conf file has a line to define that...
>>
>> It may be that he has chosen the wrong polarity, but I suspect he has
>> simply chosen the wrong options (the delay and offset options).
>>
>
> If the 1pps signal has a 50% m/s ratio, then the ~0.5second offset on
> the external sources is a glaring indicator of wrong polarity...

Yes, except most pps signals do not have a 50% ratio. More like a 10%
ratio. I do not know the UBlock gps unit so it could be weird, or maybe
he set up the UBLOCk to have a 50% ratio. Or maybe his "offset" commands
are confusing everything.
>
>