Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

Unruh wrote:
[]
> I use cat 5e cable since it is cheap, available and is supposed to be
> good for better than about 100MMHz
> (10nsec) signals. I would not use usb cable or any old wire, because
> of
> the problems of spread of the pulse from the gps. Also I would
> terminate
> it properly as well so that signal  reflections could be problematic.
> on
> long runs.
> If the run is less than 10m it should be ok even with improper
> termination.

Cat 5e cable sounds like a good compromise.  On very long runs, you would 
not only need to terminate the cable correctly, you would need to drive it 
correctly as well, requiring powered line drivers and receivers at either 
end.

In the OP's case, the run is only 30m (i.e. about 100-150ns) so the effect 
of reflections on a system (RS-232) which is bandwidth-limited to a 
microsecond or two should be very little, and I would likely use the cable 
in an unbalanced configuration.

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

Unruh wrote:
[]
> The nmea is virtually useless for accurate timing. The main thing that
> the unit gives you is the PPS. You have to makes sure you do not
> degrade it.

The GPS 18x LVC only claims an accuracy of one microsecond for PPS in the 
first place.  The RS-232 receivers may well have some filtering limiting 
the risetime to a couple of microseconds (i.e. good enough for the maximum 
baud rate, typically 115,200 baud), so even if the final risetime after 
the cable is a microsoecond or so, that's not going to degrade the 
accuracy signifcantly for normal use.  Not an issue.

>>> I'm not sure whether the NMEA driver attempts to send anything /to/
>>> the
>
> Which NMEA driver?


The one in NTP, which would work with the GPS 18x LVC.

David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

Unruh wrote:
[]
> Now you could get far better response by using the temperature of the
> computer to also correct for rate responses.

I do agree that if temperature could be included NTP could work even 
better.

David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

Rick Jones wrote:
> David J Taylor
>  wrote:
>> One suggestion might be wireless
>
> Isn't that just asking for jitter?
>
> rick jones

Have you tried it?  How much extra jitter do you see?  It would be 
interesting to see some real data.

If the choice were between plugging in a wireless system and having a 
little extra jitter, and having to pay some money for work to allow cables 
to be run.

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David Lord wrote:
[]
> I only have a pair of servers as peer and that is maxpoll 8 and
> both sat at 256 sec. Offsets are 203us and 593us.

I see more like 1-3ms for the Internet servers (compared to the GPS), with 
delays in the order of 30ms.  This is with Windows, though, not a UNIX 
system.

> I have problems with the larger maxpoll value as temperature
> changes are sometimes at a higher rate than ntpd can compensate
> for but this affects the pcs differently and having peers with
> lower maxpoll might help. Otherwise the higher maxpoll does
> seem to tend to give lower offset variation and jitter. So far
> this year I've not had temperature in back room shoot from 15C
> to near 30C as happened on a couple of days last year.
>
> David

Yes, it's the classic trade-off - high precision requires a long 
time-constant, but that means a poorer response to temperature changes. 
You have to decide when you have it "good enough", otherwise you will be 
tinkering for life!

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David Lord wrote:
[]
> I'll scope pps down utp but doubt the pps will keep its rising
> edge. I'm having a box with indicator led and 5V regulator at end
> of the stock Garmin cable and coax + utp from that box downstairs.
> One pair will have +9V/0V to the regulator. It's a long while
> since I ran an rs232 cable downstairs but remember I had problems
> with higher data rates and 38400 bps being unreliable but 9600 bps
> just ok. That was also full rs232 levels rather than ttl.

Capacitive loading may slow down the edge a little, but I would expect 
that risetimes which are similar to RS-232 risetimes would be quite fine 
for PPS use, so a smooth one microsecond edge would be just fine. 
However, 38400 bps would be 26 us wide pulses, so if you had problems with 
that, perhaps it's not good enough for PPS.  I have a 5V regulator on one 
GPS 18, but decided to use the USB 5V approach for the other and it's been 
fine.

[]
> Anyway getting better than 100us on Garmin vs better than 700ms
> with BR304 is a big enough step up already. Really all I need is
> that all pcs keep same time and several ms from utc is ok.
> Problem with ntp via broadband is sometimes a large download or
> build gives >100ms difference between servers and I expect
> feeding pps to each server will solve that problem.
>
> cheers
>
> David

With my broadband, I recall that PCs kept well within +/- 100ms, but I 
perhaps have a different usage pattern to you.  I like the idea of a 
buffered PPS feed to each server, and would be most interested to hear how 
it works out.  To be within a few ms though, having one stratum-1 server 
and the rest over the LAN would probably be adequate.  BTW: I'm using 
different minpoll and maxpoll values to have the benefit of both LAN 
stratum-1 and Internet fallback servers, without hammering the Internet 
servers too hard.


server 192.168.0.2  iburst maxpoll 6  prefer # startum-1
server 192.168.0.7  maxpoll 6  # second stratum-1

server 0.uk.pool.ntp.org minpoll 10
server 1.uk.pool.ntp.org minpoll 10



Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David Woolley wrote:
[]
> When used with proper balanced drivers and receivers, twisted pair is
> often better than coax.
>
> For any type of cable, group delay characteristics may be more
> important than characteristic impedance match.

Whilst I agree with both points, for carrying what are TTL-level signals 
with rise-times probably greater than 100ns where you are using an RS-232 
receiver to detect pulses 0.2s wide, and over a distance or 30m (i.e. a 
time of around 100-150ns), almost any cable will do.  The only exception I 
might make is where the environment is electrically noisy - i.e. an 
industrial setting or running behind a photocopier, air conditioner, heavy 
motor or similar, where I would want at least shielded cables.

I say this from years - too many years! - experience with RS-232.

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David Lord wrote:
> I'm intending buffering the pps to give 75r output to coax with
> another converter back to ttl at the server. The NMEA should manage
> the distance over twisted pair at 4800 baud.
[]
> I'd rather have the option for two way in case the Garmin needs to be
> set to a different mode. I have a reel of utp I think should do.
>
> I'll have some sort of fan-out box to get a pps signal to each of
> servers that are powered up continuously.
>
> I've now seen an error in ntp log and suspect pps isn't enabled in
> kernel by default (NetBSD-5). I'll check tomorrow.
>
> Cheers
>
> David

David, if you have UTP cable, I think that's four twisted pairs, so I 
would just use one pair per signal (TX, RX, PPS)  and the remaining pair 
as an earth/+5V.  Unless you have a noisy electrical environment, I think 
that will be fine over 30m.  Screened would be better, if you have it. 
Fan-out would be nice - I've used two RS-232 input in parallel fed from 
one GPS 18 without problems.

I thought the offset figures you were quoting were for Windows - 
"between -74us and +62us".  For a PPS signal on a FreeBSD system I would 
expect much better.  I recall needing both the NMEA and the ATOM driver 
configured.  Oh, yes, I vaguely recall having to compile the kernel as 
well.  It was a few years ago
  http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David Lord wrote:
[]
> Late last night I got round to connecting the Garmin GPS18x-LVC and
> just after midnight it stepped from around 60s to 0.5ms and 8 hours
> later is between -74us and +62us. The module is in south facing
> upstairs window in same location I failed to get anything useful
> from the Globalsat BR304. Now I need to make a 30m extender cable to
> get the signals downstairs to back of house to connect to servers.
>
> David

Good news, David.  Sensitive little pill-box, isn't it?

One suggestion might be wireless - could you get a very atom-based small 
PC or even a wireless router to accept the GPS signal and serve NTP over 
the WLAN?  Cable would be nicer and my preference.  With Dave Hart's new 
PPS support it /should/ be possible to send just the PPS signal around 
(two wires), and use that to refine an Internet-derived time.  I might be 
inclined to go for a screened cable if you need a 30m run, but thin 3-core 
mains cable /might/ suffice.  The RS-232 I used to use was very tolerant 
of cabling, but it probably had higher signal levels and robustness than 
the GPS 18x LVC.

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David J Taylor wrote:
[]
> I might be inclined to go for a screened
> cable if you need a 30m run, but thin 3-core mains cable /might/
> suffice.

I'm not sure whether the NMEA driver attempts to send anything /to/ the 
GPS device.  If not, three lines might to (ground, TX from GPS, PPS), 
otherwise four lines are required.  If you want to take USB power from the 
server (as I now do), it's five lines minimum.

Cheers,
David 

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[ntp:questions] ntpd not responding to IPv6 queries?

[David J Taylor]

I have ntpd 4.2.4p6 running on a Windows 7 RC machine.

>From the command prompt, when I enter:  ping , ping works 
correctly, but seems to be using an IPv6 address.  I guess this must be an 
auto-assigned address, as I have no IPv6 network as such.  If I enter: 
ntpq -c rv , I get the error message:

  ntpq: read: no such file or directory

This PC is primarily an IPv4 pc, and if I enter the command with the IPv4 
numeric address:  ntpq -c rv 1.2.3.4, it works as expected.  If I add an 
entry to etc/hosts  1.2.3.4 pc-name,  the ntpq -c rv  works 
correctly

I can't reproduce the problem on a Windows Vista PC running ntp 4.2.5p181.

So, with PCs having both IPv4 and IPv6 running, is there a difference 
between ntp 4.2.4 and 4.2.5 which would explain such behaviour?

Thanks,
David 

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Re: [ntp:questions] NTP 4.2.5p181 supports PPSAPI provider DLLs on Windows

[David J Taylor]

Dave Hart wrote:
[]
> NTP 4.2.5p181 binaries for Windows are at:
>
> http://davehart.net/ntp/win/x86/
> http://davehart.net/ntp/win/x86/ntp-4.2.5p181-win-x86-bin.zip
> http://davehart.net/ntp/win/x86/ntp-4.2.5p181-win-x86-debug-bin.zip
>
> Cheers,
> Dave Hart

The "release" version is installed and running on Windows Server 2000, 
Windows XP Home, Windows XP Pro, Windows Vista, and Windows-7 RC.  The XP 
Pro and the Windows 2000 systems are also running serial-PPS (atom) DLL, 
with the March serialpps.sys, providing the more accurate kernel-mode 
timestamps.  Results (as they accumulate) will appear here:

  http://www.satsignal.eu/mrtg/daily_ntp.html

Excellent work, Dave, many thanks.

David 

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

newsreade...@web.de wrote:
[]
> Hi Dave, hi community,
>
> I have a setup where the serial data is - for technical reasons -
> routed over a LAN via 16 port MOXA port servers. While in general I
> found that ntp gets along well with the virtual ports, 4.2.5p180 seems
> to fail to connect once the com port number is 2 digits. in my
> hardware com1-com3 are hardware, com4-com19 are emulated by the MOXA
> driver software. NTP conencted well to com6, com8 and com9, but did
> not connect to com10 or higher.
>
> AL.

AL,

I think Dave Hart is doing further work in this area, so I hope he can 
help.

Cheers,
David 

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Re: [ntp:questions] .1 Microsecond Synchronization

[David J Taylor]

ScottyG wrote:
[]
> What do you think you can achieve with let say 5,000-10,000 USD
> budget for each data center? Could we get 1 micro, 10 micro, 100
> micro, 1 milli?
>
> One catch is the not all the data centers have access to roof space
> for us. One company claims that they can use CDMA as a source time.
> Does anyone know the implications of this? It seems that the time
> would be sourced from GPS and retransmitted via the cell towers. To
> me this brings up more potential delays but I am not an expert.
>
> Scott

Scott,

On servers with a direct connection to a PPS (GPS) reference source, 10us 
may be possible, but if that server is heavily loaded it might deteriorate 
to 100us.  If the server is running Windows then 1ms.  Constancy of 
temperature also matters for the greatest accuracy.

You seem to be implying that this is not all under your control, and that 
you would need to trust third parties.

Cheers,
David 

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Re: [ntp:questions] NTP 4.2.5p180 adds IPv6 support on Windows

[David J Taylor]

Maarten Wiltink wrote:
[]
> As it happens, I recently had cause to install a clean Windows
> somewhere and downloaded what turns out to be vegas-v2. As of five
> minutes ago,
> a new NTP is gathering loopstats.
>
> Thanks!
>
> Groetjes,
> Maarten Wiltink

That's good news, Maarten.

So, one question which now arises is:  how should the current Windows NTP 
handle the libeay32.dll version issue?  Having it packaged with Meinberg's 
distribution, and putting it into the application directory seems to be an 
approach which works.

Should those installing by copying ntpd.exe etc. from Zip archives be 
expected to look after libeay32.dll themselves?  Should the bindings be 
dynamic rather than static so that ntpd can fall back if the required 
entry point or even the DLL isn't available?  Should the "correct" version 
of libeay32.dll always be included with the Zip archive?

Cheers,
David 

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Re: [ntp:questions] Dave Hart Windows PPS patch set and Atom driver

[David J Taylor]

hven...@astound.net wrote:
> Just a quick follow up.  Dave has supplied me with some updated code
> and this seems to be working OK on my machine now.  It appears that
> most of the issue I was seeing was corrected when I turned serial port
> buffering off.  At this point I am using the Atom (PPS) driver on
> Windows since the Oncore driver is not working at this time.

Thanks for reporting back.  Good of Dave to find time to help, and good 
that we are gradually extending the Windows support in NTP.  My thanks to 
all that are helping.

David 

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Re: [ntp:questions] NTP 4.2.5p180 adds IPv6 support on Windows

[David J Taylor]

Maarten Wiltink wrote:
[]
> A Windows 2000 without IPv6 says 'Ordinal not found : The ordinal 3852
> could not be located in the dynamic link library LIBEAY32.dll.'
>
> Copying the DLL into the directory didn't help, either.
>
> Groetjes,
> Maarten Wiltink

What libeay32.dll do you have?  Mine is dated 13-Jan-2009, and is 
1,105,392 bytes.  file version 0.9.8.10, product version, 0.9.8j (I 
think).  It's in the ntp\bin\ directory.  ntpd.exe is working fine - 
Windows 2000 server, no IPv6.

Cheers,
David 

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Re: [ntp:questions] NTP 4.2.5p180 adds IPv6 support on Windows

[David J Taylor]

Maarten Wiltink wrote:
[]> It came with NTP-4.2.0 Windows binaries dated 2003-10-17. The DLL is
> dated 2003-06-04, 827 392 bytes, no version information.
> 
> Groetjes,
> Maarten Wiltink

The newer file is here if you need it:

  http://www.satsignal.eu/libeay32.zip

Cheers,
David

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Re: [ntp:questions] NTP 4.2.5p180 adds IPv6 support on Windows

[David J Taylor]

Maarten Wiltink wrote:
> "David J Taylor"
>  wrote
> in message news:qzaul.35766$oo7.25...@text.news.virginmedia.com...
>> Maarten Wiltink wrote:
>
>>> A Windows 2000 without IPv6 says 'Ordinal not found : The ordinal
>>> 3852 could not be located in the dynamic link library LIBEAY32.dll.'
>>>
>>> Copying the DLL into the directory didn't help, either.
>
>> What libeay32.dll do you have?  Mine is dated 13-Jan-2009, and is
>> 1,105,392 bytes.  file version 0.9.8.10, product version, 0.9.8j (I
>> think).  It's in the ntp\bin\ directory.  ntpd.exe is working fine -
>> Windows 2000 server, no IPv6.
>
> It came with NTP-4.2.0 Windows binaries dated 2003-10-17. The DLL is
> dated 2003-06-04, 827 392 bytes, no version information.
>
> Groetjes,
> Maarten Wiltink

Maarten,

The one I have is from the VegasV2 release, and is more recent.  If you 
don't have that somewhere, I could e-mail it.

Cheers,
David 

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Re: [ntp:questions] NTP 4.2.5p180 adds IPv6 support on Windows

[David J Taylor]

Dave Hart wrote:
> You can find binaries at:
>
> http://davehart.net/ntp/win/x86/ntp-4.2.5p180-win-x86-bin.zip
> http://davehart.net/ntp/win/x86/ntp-4.2.5p180-win-x86-debug-bin.zip
>
> Testing on the earliest supported versions of Windows has been light.
> My binaries unfortunately are unable to load on Windows NT 4, at all
> due to the compiler dropping support,
> but I'm particularly interested in results on Windows 2000, with or
> without the IPv6 stack installed.
>
> Cheers,
> Dave Hart

Dave,

I've installed the release version (just ntpd.exe) on my Windows 2000 
Server PC, Bacchus, without an IPv6 stack (as far as I know).  It appears 
to install and run correctly, although there were two errors reported in 
the event log:

30/05/2009 06:37:45 NTP Error None 1 N/A BACCHUS setsockopt(208, 
SO_EXCLUSIVEADDRUSE, on): Invalid argument

30/05/2009 06:37:45 NTP Error None 1 N/A BACCHUS setsockopt(216, 
SO_EXCLUSIVEADDRUSE, on): Invalid argument

I will e-mail you the full event log.  The performance can be seen here 
(eventually):

  http://www.satsignal.eu/mrtg/bacchus_ntp-b.html

Cheers,
David 

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Re: [ntp:questions] GPS jamming - Wales: 7-11 & 14-18 September 2009

[David J Taylor]

David J Taylor wrote:
> For your information:
>
> ___
> The MoD has informed Ofcom of the following GPS jamming exercise:
>
> Dates: 7-11 September and 14-18 September 2009.
>
> Times: limited periods between 09:00 and 17:00 hrs
>
> Location: Within 5km of N52° 00.881' and W003° 38.518' (Sennybridge
> Training Area, Mid-Wales).
>
> Contact: Trial Manager (during the trial) on 07766 134520 or the 24hr
> Sennybridge Operations point on 01874 635461.
> ___

Sorry about the wrong date!

David 

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[ntp:questions] GPS jamming - Wales: 7-11 & 8-18 September 2009

[David J Taylor]

For your information:

___
The MoD has informed Ofcom of the following GPS jamming exercise:

Dates: 7-11 September and 14-18 September 2009.

Times: limited periods between 09:00 and 17:00 hrs

Location: Within 5km of N52° 00.881' and W003° 38.518' (Sennybridge 
Training Area, Mid-Wales).

Contact: Trial Manager (during the trial) on 07766 134520 or the 24hr 
Sennybridge Operations point on 01874 635461.
___


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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

David Lord wrote:
[]
> I eventually ordered from gpsw.co.uk, UKP 71.02 inclusive. I'd
> searched their site prior to trying the US ones and not been able to
> locate the GPS 18x-LVC and only went back after it being confirmed
> here they stocked the product.

I also ordered from  GPS warehouse and it arrived very quickly.
  http://www.gpsw.co.uk/details/prod2402.html

> I've not yet connected the GPS 18x as still thinking about where to
> mount it. I previously tried with a BR304 without pps and had 80%
> of time +/- 25ms, much worse than for time from internet whilst a
> Conrad DCF module used over a few days gave 80% at +/- 2ms, better
> than expected, but both BR304 and DCF have reception difficulties.
>
> David

Mine is now sitting indoors, near the roof of an upstairs room.  It's a 
lot more sensitive than the plain "18" model, so I'm trying it indoors 
rather than on the roof  (where my 18 lives).  It's a backup, and working 
into a rather poor Windows box, but keeping generally within 0.5ms.

  http://www.satsignal.eu/mrtg/stamsund_ntp_2.html

I couldn't see any change between the outdoors 18 and the indoors 18x on 
that PC.  The changeover was on Friday, May 22, week 21 - spot any 
difference?

Cheers,
David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

piste...@start.no wrote:
[]
> When calculating NOK to USD, I end up with $152,24. That's actually
> more than double the $63 price you have seen in US!! If I found a US
> place selling it for $63 I suppose it should get quite a lot cheaper
> even when adding shipping and tax.
>
> Geir

.. except that many American suppliers will not ship outside the US. 
Probably still worth getting, though, at NOK ~800.

David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

Unruh wrote:
> piste...@start.no writes:
[]
>> Actually the Garmin 18x LVC is quite expensive here in Norway? Seems
>> like it's quite a lot cheaper abroad, but with tax and postage I
>> don't think it's any cheaper to order one unit from US or
>> somewhere...
>
> How much is "quite expensive" It should be about US$100.

In the UK the base price, without tax, is GBP 56.98 (~ US $91)

With tax and delivery it was GBP 71.02 (~US $113)

I also feel this is quite expensive, as some base prices are down to US 
$63

  http://shopping.aol.com/garmin-gps-18x-lvc-receiver-12-channels-/75700944

David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

Unruh wrote:
[]
> Probably better than 10 microseconds from the PPS if you had a decent
> operating system (eg BSD or Linux) On windows, maybe 1 msec
> accuracy.\.

More like better than 200 microseconds on a good Windows 2000 or XP 
system, even in a non-temperature-controlled environment, when running on 
a non-interactive system.

  http://www.satsignal.eu/mrtg/feenix_ntp_2.html

David 

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Re: [ntp:questions] NMEA ref.clock better than my ISP's timeserver?

[David J Taylor]

piste...@start.no wrote:
> After first trying the Haicom HI-204III claiming to have PPS in the
> manual without really having it, I bought a Garmin 18x LVC and
> connected it to the onboard COM-port (COM1) on my Asus M3N78 PRO
> mainboard. The Haicom is residing on a USB serial adapter (COM6) to
> check how stable the offset is.
>
> Running ntp4.2.5p175-win-x86-bin configured with a couple of
> timesources it seems like my ISP's NTP-server gets "disqualified".
> Before setting up my own ref.clock I used to have ntp.online.no as my
> "favorite NTP-server" thinking it would be the best / most local
> server, but now I might offer them to use me as a clock-source? ;)
>
> Anyone wishing to see on their own, might check with ntpq
> solbakken.dyndns.org   What kind of accuracy is expectable with a NMEA
> GPS with PPS connected to the DCD-line of the serial port? It's not
> that I have any special need for extreme accuracy, but I suppose it's
> allright having the most accurate clock in the neighborhood. :)
>
>
>
> Cheers,
> Geir F

Geir,

I typically see an offset within 0.2 milliseconds using a direct 
connection:

  http://www.satsignal.eu/mrtg/feenix_ntp_2.html

With USB I would see within about 0.5 milliseconds.

Both are much better than an Internet-based time source.

Your Haicom has an offset of nearly 0.5s, suggesting that you might be 
using the wrong edge of the PPS signal.

Cheers,
David 

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[ntp:questions] NTP Loopstats plotting program updated

[David J Taylor]

Folks,

I've updated my NTP Loopstats plotting program for Windows in a number of 
ways, including the overlay of offset and relative frequency error for 
each 24-hour period.  Please see:

  http://www.satsignal.eu/software/net.htm#NTPplotter

It allows a clearer view of daily temperature or other effects.

Cheers,
David 

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Re: [ntp:questions] strange time behaviour

[David J Taylor]

vhfme...@t-online.de wrote:
> Hello,
>
> I have an embedded application running under Linux 2.6.22 #1 PREEMPT
> with 1000 ticks per second (PC architecture, AMD Geode Processor).
> Since precise timing is needed, the devices are synchronized to a time
> server via ntpd 4.2.2p4.
>
> After running 48 days and 13 hours without problems, things got crazy.
[]
> I have no idea, what the problem is. Does anybody know, what's going
> on and how to cure it?
>
> Regards, Volker Meyer

1165 hours - 2^32 milliseconds.

Sounds like something rolled over.

Supposedly this was once a Windows problem, although I've never 
encountered it.  You are reading a millisecond value with a 32-bit 
counter, and it's top bit is overflowing.

Don't run Linux here, Volker, so I can't suggest a solution.

Cheers,
David 

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Re: [ntp:questions] Loopstats updated less frequently than expected

[David J Taylor]

Unruh wrote:
[]
> If you mean you have a refclock attached, they have round trip time of
> 0. Thus there is never a minimum and all get used. Ntp's algorithm in
> short is: Save the last 8 polls. Check if the current poll has a
> larger
> roundtrip time than any of those 8. If it does, do not use it.
> If the round trip times are all 0, then the current one is never
> larger
> so it is always used.
>
> Now, the round trip time on the net  is a random variable, but from
> experience, on average only about 1 in 8 are used. ( actually it is a
> bit better than
> that so that about 1/7  are actually used.)
>
> This is to avert bias on the theory that longer round trip times are
> probably biased (  the delay is caused by one of the legs being
> longer than the other), but as a result, the actual average poll
> interval is
> roughly 7 times longer than the requested interval. Also since the
> time
> constants must be longer than the longest poll interval, this helps
> the system
> to have a very long time constant (ie respond extremely slowly to
> changes).

That makes some sense, Bill, and probably more if I study it more 
carefully.

Thanks,
David 

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Re: [ntp:questions] Loopstats updated less frequently than expected

[David J Taylor]

Unruh wrote:
[]
>> As I have maxpoll set to 6, I would have expected entries no more
>> than 64s apart.  What am I failing to understand here?  The poll
>> values reported in ntpq -p are 64, 64 and 1024 - as expected.
>
> You are forgetting that ntp throws away 7/8 of the stuff it collects.
> (This is in an attempt to counter round trip biases).
> Thus you would expect to have 8 times the max poll interval between
> loopstats. (it is random so it is not always exactly 8 times sometimes
> less, but never more, but it averages out to pretty close to 8 times.)

Thanks for that, Bill.  With the servers with a GPS directly attached, I 
typically get 5400 lines in the log file, for a 16s polling interval. 
That's one line per poll, not one line per approximately eight polls.

Cheers,
David 

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[ntp:questions] Loopstats updated less frequently than expected

[David J Taylor]

Folks,

I have the following entries in ntpd.conf:

server 192.168.0.2  iburst maxpoll 6
server 192.168.0.7  maxpoll 6
server 0.uk.pool.ntp.org minpoll 10

.. and the following as the most recent loopstats:

54974 37901.029 -0.000209922 13.840 0.000108471 0.007233 6
54974 38229.033 0.000346890 13.846 0.000221473 0.007179 6
54974 38754.041 -0.000217131 13.840 0.000287548 0.007132 6
54974 38954.047 -0.91306 13.839 0.000272631 0.006682 6

I note that the times between these four entries are:

328s
525s
200s

As I have maxpoll set to 6, I would have expected entries no more than 64s 
apart.  What am I failing to understand here?  The poll values reported in 
ntpq -p are 64, 64 and 1024 - as expected.

Thanks,
David 

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Re: [ntp:questions] New Version of NTP Installer for Windows from Meinberg

[David J Taylor]

Dave Hart wrote:
> David J Taylor:
>> Does this new release include the improved interpolation developed
>> by Dave Hart, and the Windows Vista/7 optimisations?
>
> No, those are only in 4.2.5p162 and later.  See
> http://bugs.ntp.org/216 Very soon a release candidate cycle for 4.2.6
> should start, so it shouldn't be terribly long before a -stable NTP
> release includes the new Windows interpolation code.  4.2.4p7 does
> have substantial improvements vs 4.2.4p6 in the Windows serial code
> used by, for example, the NMEA reference clock driver.  However,
> lacking the 216 fix, it's not really a good choice for any upstream
> server duty, though it's great as a client assuming better than 1
> millisecond accuracy is unimportant.

Thanks, Dave.  Looking forward to 4.2.6!

>> You may know that I discovered a problem with Windows 2000 afer bug
>> fix 1149. Is the Windows 2000 fix 1191 included?
>
> Yes it is.  Heiko also identified and fixed in the Meinberg release a
> problem building current NTP (-stable and -dev) using the now-ancient
> Visual C++ 6 compiler.  Anyone attempting to build from source using
> VC6 should see http://bugs.ntp.org/1196 for the solution.  I would
> appreciate contact from anyone building NTP using VC6, as I believe
> only Meinberg and possibly Danny Mayer are still using it with NTP.  I
> hope to see support for VC6 dropped before too much longer, as it
> requires some ugliness in the code to work around half-implemented 64-
> bit scalar support.
>
> Cheers,
> Dave Hart

That's good to hear.

If it were possible to keep Visual Studio 2005 support that would be 
"nice", as it might allow me to try building NTP here once again.  Not 
eseential, though.

Cheers,
David 

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Re: [ntp:questions] New Version of NTP Installer for Windows from Meinberg

[David J Taylor]

Heiko Gerstung wrote:
> Hi Clock Addictives,
>
> following the security update of NTP we built a new version of our NTP
> Installer for Windows which now installs NTP 4.2.4p7 (ntpd and tools)
> as well as the full NTP Documentation. The installer now also
> includes the current version of the OpenSSL library (0.9.8k).
[]
> The new version has been nicknamed "copenhagen" because I am going to
> spend my summer vacation with my family in Denmark this year. I am not
> quite sure if we will make it to Copenhagen, though.
[]
> Regards,
>  Heiko

Heiko,

I'm sure you'll enjoy Denmark - you can also visit Copenhagen near 
Christmas.  All ages enjoy the Tivoli Gardens, as perhaps you know.  I do 
hope you get there.

Does this new release include the improved interpolation developed by Dave 
Hart, and the Windows Vista/7 optimisations?

You may know that I discovered a problem with Windows 2000 afer bug fix 
1149.  Is the Windows 2000 fix 1191 included?

Windows users will welcome your work and these improvements.  Thanks for 
making the installation available.

Cheers,
David 

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Re: [ntp:questions] Query about NTP accuracy

[David J Taylor]

Richard B. Gilbert wrote:
[]
> I'm not sure that ANYTHING, other than a local atomic clock, is going
>  to get you microsecond accuracy.  10 milliseconds is probably
> attainable for other than Windows clients.  The Windows clock ticks
> every 17 milliseconds and may be accurate to within a few hundred
> microseconds but, given the available resolution, you have no way to
> determine if it is that accurate.

Gerneally agreed, although Windows /can/ do within perhaps 3 milliseconds 
with NTP and a stratum-1 server on the same LAN:

  http://www.satsignal.eu/mrtg/bacchus_ntp-b.html

  http://www.satsignal.eu/mrtg/narvik_ntp-b.html

  http://www.satsignal.eu/mrtg/hydra_ntp-b.html

when running continuously, although not when running certain USB devices 
which seem to affect NTP rather badly:

  http://www.satsignal.eu/mrtg/gemini_ntp.html

Cheers,
David 

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Re: [ntp:questions] Query about NTP accuracy

[David J Taylor]

Andy Yates wrote:
> Does anybody have any figures that shows the effect on accuracy of an
> NTP v3 client using a stratum 1 server rather than a stratum 2 or 3
> server? It's all in a GE LAN based scenario, commercial stratum 1
> servers connected to GPS and stratum 2 and 3 servers are typically
> dedicated Linux boxes.
>
> The reasons is that I would rather scale by adding strata - its a very
> big data center with thousands of clients and has several "zones" that
> are isolated. However some opinion is suggesting we run IRIG-B between
> the GPS receiver and a bunch of stratum 1 servers and clients access
> these directly. Much more expensive and any increase in accuracy from
> a client experience may be negligible.
>
> However I'm been pressed to supply an SLA for accuracy. My argument is
> that although you can get your stratum one server to synchronize to
> microseconds of UTP, as soon as the client uses NTP v3 over the LAN,
> even a GE LAN, then the accuracy degrades and putting well designed
> well specified stratum between the boxes is not going to decrease
> accuracy sufficiently to warrant purchasing many stratum one
> appliances.
>
> Thoughts?
>
> Regards
> Andy

Andy, I think your approach is correct - no extra stratum-1 boxes.  As 
Richard implies, the load on the network to the clients is perhaps the 
most important factor in accuracy.

Questions:

- why are you still using NTP v3?  Isn't that rather old now?

- what accuracy do your clients actually need?  Are they Windows PCs or 
some other OS?

Cheers,
David 

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

Dave Hart wrote:
> On May 14, 7:27 am, "David J Taylor" wrote:
>> It would indeed be interesting to see how well it performed, either
>> with FreeBSD or with Windows. I don't know if a USB/GPS driver is
>> available with the present version of NTP.
>
> No special driver is required for USB GPS receivers which present as
> standard serial devices and can be configured to generate a supported
> NMEA sentence once per second.  I know of one person who tested this
> approach on Windows, and as I recall the performance was worse than
> internet sources with that particular hardware.
>
> Cheers,
> Dave Hart

Dave,

I believe that my GPS (for example) does not present itself in this way (I 
don't see it listed as a COM port device), so I wondered whether a special 
driver might be required for it.  Completely agreed that if it /does/ 
appear as a serial port, no problems.  You would still miss out on the PPS 
line, though, wouldn't you?

Cheers,
David 

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

John Hasler wrote:
> David wries:
>> .. but if something only needs millisecond timing, designing for
>> nanosecond accuracy is gross over-engineering, and likely rather
>> costly. 
> 
> There's no real cost: just a few bytes in a data structure.  Better
> to have it and never need it then to leave it out and later find it
> necessary. It's just room for expansion.

The cost depends on the system.
An atomic clock versus a quartz crystal, for example.

David

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

David Woolley wrote:
[]
> The problem with USB latency is that it is unpredictable.  The
> uncertainty in the direct serial port latency is 1/16 th of the
> signalling unit length (about 6 microseconds at 9600) plus the
> uncertainty in the interrupt and process scheduling latencies.  (If
> the UART clock is free running on the GPS device, you might need to
> add another 1/16th, so about 12 microseconds.)

Thanks, David.  As NTP deals well with the unpredictable latency on the 
internet, it's not impossible that a USB/GPS device could produce 
significantly better results than a consumer internet connection alone.

I'd like to see actual NTP results.

Cheers,
David 

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

Augustine wrote:
> On May 9, 2:17 am, "David J Taylor"  part.nor-this.co.uk.invalid> wrote:
>>
>> Background: I have a GPS 18 and USB
>> serial converter, and I wanted to see how well that actually
>> performs.
>
> Very interesting experiment.  May I suggest using USB directly?
>
> TIA

Augustine,

You may indeed suggest that, but the key point here is (I think) that the 
USB/serial preserves the PPS (pulse per second) signal from the RS-232 
connection, and it is the PPS signal transition which is used provide the 
precision part of the timing.

I understand that USB alone will typically not have any PPS information, 
so the timekeeping accuracy would be just that of the serial port 
messages, degraded by whatever USB latency adds, but improved by the fact 
that the messages are much shorter on USB than on serial.

It would indeed be interesting to see how well it performed, either with 
FreeBSD or with Windows.  I don't know if a USB/GPS driver is available 
with the present version of NTP.

Cheers,
David 

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

Unruh wrote:
[]
> Well, I call "good" to include the design. If a car is designed so
> that
> the wheels fall off every 100 miles, no matter how closely the car
> meets
> the design, it is a bad car.

.. but if something only needs millisecond timing, designing for 
nanosecond accuracy is gross over-engineering, and likely rather costly.

David 

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

Unruh wrote:
[]
> Since the same machine can run Linux or BSD whose resolution is usec
> or
> nsec, yes, the hardware can do better. The question is how good is the
> software in the kernel. If I do a timestamp on an event, how accurate
> is
> that timestamp?
> Is it msec? Is it 15msec?

The precision with which a standard Windows system call returns the 
current time will be 1 millisecond.  The value reported by that call may 
step in 1, 10 or 15ms steps depending on the version of Windows you use, 
and whether you turn on the "fast" timer (the multi-media timer).

I am running ntp on windows and it is reporting offsets of a fraction of a 
millisecond, so does that mean that the milliseconds reported are within a 
millisecond of UTC?

It's not a matter of "how good" is the kernel, it's what the design 
specifications are, if I understand it correctly, and the design specs for 
different versions of Windows are different.

Cheers,
David 

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
>
>>
>> - with operating system calls, the main clock can be read with a
>> precision of 1 millisecond (although the ticks may be only 15
>> milliseconds).  There are higher resolution counters which can also
>> be read.
>
>
> The architectural resolution is much higher than this.  I think you
> are seeing actual 1ms clock ticks, as the result of ntpd forcing the
> use of multi-media timer mode.

David, yes the hardware is better, but I was asked what the system clock 
call was and the structure it returns only goes down to milliseconds. 
See:

  http://msdn.microsoft.com/en-us/library/ms724390(VS.85).aspx

  http://msdn.microsoft.com/en-us/library/ms724950(VS.85).aspx

I'm not "seeing" anything.

Cheers,
David 

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

Unruh wrote:
[]
> OK, I keep forgetting. What accuracy can the clock be read on windows?
> is there an interpolation routine in the kernel so the clock can be
> read
> to usec accuracy?
> I would thin k you could set up and interrupt routine to read and
> record
> the clock time when the interrupt occurs.

Bill,

- with operating system calls, the main clock can be read with a precision 
of 1 millisecond (although the ticks may be only 15 milliseconds).  There 
are higher resolution counters which can also be read.

- yes, for NTP's internal use there is an interpolation routine, recently 
updated by Dave Hart.

- yes, Dave Hart has a modified device driver which records the time in 
kernel mode, rather than the more usual user-mode timestamping.  On my 
main stratum-1 PC, this reduced the jitter reported by NTP (and averaged) 
from around 5 microseconds to around 2.2 microseconds.

Cheers,
David 

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

Unruh wrote:
> "David J Taylor"
[]
>> On my system, I can detect no difference between the GPS 18 and the
>> GSP 18x.  I am looking at jitters in the order of 2.2 microseconds,
>> and offsets in the range +170/-100 microseconds.
>
> How are you reading the PPS interrupts>. That offset is terrible. On
> my PPS feeding a parallel interrups, the offsets are less than 10us.

This is a Windows system, Bill.  I know I would do far better with a 
FreeBSD system (I used to get better than 20microsecond offsets), but I'm 
able to run one PC less now, by having a Windows PC as my stratum-1 
server.

The offset is more than good enough for my purposes.

Cheers,
David

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Re: [ntp:questions] best gps receiver for time synchronization

[David J Taylor]

Hal Murray wrote:
[]
> If anybody has figured out how to get good timing out of the
> SiRF units, please clue me in.

On my system, I can detect no difference between the GPS 18 and the GSP 
18x.  I am looking at jitters in the order of 2.2 microseconds, and 
offsets in the range +170/-100 microseconds.

Cheers,
David 

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Re: [ntp:questions] How bad is USB?

[David J Taylor]

David Malone wrote:
> "David J Taylor"
> 
> writes:
>
>> I know it's off-topic, but how far apart in time does two singers, or
>> choir, have to be before you notice?  (No, I'm not suggesting a
>> spoken ref clock  ).
>
> If you have an small orcestra between a conductor and choir, the
> choir can be a good bit behind the conductor unless they watch
> rather than listen. This is probably only a matter < 10m (though
> I suspect the effect is not just due to the speed of sound, but
> also due to the compounding of people's reaction times).
>
> David.

So given the speed of sound, that must be less than 30ms, and within the 
10-100ms range which Bill gave.

So far, my USB-synced clock seems to be within a millisecond, so certainly 
better than just using an Internet connection (at least with /my/ Internet 
connection).

Thanks,
David 

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Re: [ntp:questions] How bad is USB?

[David J Taylor]

Unruh wrote:
> "David J Taylor"
[]
>> I know it's off-topic, but how far apart in time does two singers, or
>> choir, have to be before you notice?  (No, I'm not suggesting a
>> spoken ref clock  ).
>
> 10-100ms
> (3-30 m)
> iThat is why speakers often make intelligibilty worse not better.
> (the speaker sound gets to you before the direct sound.)

Yes, I know that professional audio systems may have delays to the 
speakers to compensate for such effects.  How much easier that must be 
today with digital rather than analogue!

Thanks,
David 

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Re: [ntp:questions] How bad is USB?

[David J Taylor]

Uwe Klein wrote:
> David J Taylor wrote:
>> Richard B. Gilbert wrote:
>> []
>>
>>> You can try it and see what happens!  The results may be
>>> sufficiently good for your purposes.  You will almost certainly not
>>> get microsecond accuracy.  If you are willing to settle for +/- 10
>>> milliseconds you can almost certainly get that.
>>
>>
>> Richard,
>>
>> My first tests show within a millisecond or so:
>>
>>  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html#usb
>>
>
> Do I see a (sawtoth) beat signal between "true" time and the
> nominally 1ms polling interval from the usb bus?
>
> uwe

Uwe,

I don't think so.  If you mean the sawtooth on the left, peaking at 1600 
the first day and 0800 the second, that's pure temperature variation.  PC 
Narvik was not switched to USB/serial until about 1530 on day 2.  There is 
an increased fine-grain variation in the offset after the change, but the 
jitter reported by NTP has dropped from 110-140 microseconds to about 45 
microseconds after the switch from LAN-sync to USB-serial-ref-clock.

There are more performance graphs here:
  http://www.satsignal.eu/mrtg/performance_ntp.php
  http://www.satsignal.eu/mrtg/daily_ntp-p.html

Cheers,
David 

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Re: [ntp:questions] How bad is USB?

[David J Taylor]

Richard B. Gilbert wrote:
[]
> You can try it and see what happens!  The results may be sufficiently
> good for your purposes.  You will almost certainly not get microsecond
> accuracy.  If you are willing to settle for +/- 10 milliseconds you
> can almost certainly get that.

Richard,

My first tests show within a millisecond or so:

  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html#usb

Caveat: the minpoll is 16s for the USB ref-clock configuration, and 64s 
for the LAN-connect to stratum-1 system.

Cheers,
David 

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Re: [ntp:questions] Performance of serial-over-USB ref-clock

[David J Taylor]

David J Taylor wrote:
> Folks,
>
> Thanks to your help, I got the serial-over-USB GPS NMEA ref-clock
> working with Windows.  It will be interesting to see whether the
> performance is any different to a LAN connection to a ref-clock.  See:
>
>  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html#usb
>
> over the next 24 hours.  The change on PC Narvik was at 15:45 UTC,
> Saturday, May 09.
>
> Cheers,
> David

My conclusion is that there is a substantial improvement over a LAN 
connection, but that connecting via USB is not as good as a direct 
connection (as expected).  Certainly better than not having a reference 
clock.  Please see the page above for details.

Cheers,
David 

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Re: [ntp:questions] How bad is USB? (was: Re: Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.)

[David J Taylor]

Hal Murray wrote:
[]
> USB is polled by the host.  That gives it a bad reputation.
>
> But that polling is done by hardware.  The basic time scale is 1 ms.
> If you don't get your low-latency stuff sorted out on a serial port
> you can easily introduce delays longer than 1 ms.
>
> If you want microseconds, USB won't work.
>
> I've been experimenting with low cost GPS gadgets.  I haven't found
> anything great.  A main problem is that the software on most of
> them is setup for navigation rather than timekeeping.  Some/many
> of them send the serial text from a 100 ms timer so the USB
> delays are lost in the noise.
>
> Note that the Garmin 18x has this problem where the 18 didn't.
>
> I haven't tried grabbing PPS over USB.

Thanks, Hal.  I now a test setup with a GPS 18 LVC (not the "x" version) 
connected as a ref-clock via a Sitecom USB-to-serial converter.  The 
results are here, being updated every 30 minutes:

  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html#usb

I hope it's using the PPS, but I don't know the status bits well enough. 
Here's what I get:

__
C:\>ntpq -c rv
associd=0 status=0415 leap_none, sync_uhf_radio, 1 event, clock_sync,
version="ntpd 4.2.5p...@1.1825-o Apr 02 11:57:05.06 (UTC-00:00) 2009 
(9)",
processor="x86", system="Windows", leap=00, stratum=1, precision=-22,
rootdelay=0.000, rootdisp=0.992, refid=GPS,
reftime=cdb02b98.382eb6a0  Sat, May  9 2009 17:19:36.219,
clock=cdb02ba5.6d93cbf6  Sat, May  9 2009 17:19:49.428, peer=25071,
tc=4, mintc=3, offset=0.514, frequency=11.026, sys_jitter=0.039,
clk_jitter=0.038, clk_wander=0.008
__


I'm suspcious about "sync_uhf_radio", but of my two other ref-clocks with 
GPS, the one with the atom driver says: "status=2144 leap_none, sync_33", 
and the one without the ATOM driver says: "status=0415 leap_none, 
sync_uhf_radio".  Maybe they are both wrong?

Cheers,
David 

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[ntp:questions] Performance of serial-over-USB ref-clock

[David J Taylor]

Folks,

Thanks to your help, I got the serial-over-USB GPS NMEA ref-clock working 
with Windows.  It will be interesting to see whether the performance is 
any different to a LAN connection to a ref-clock.  See:

  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html#usb

over the next 24 hours.  The change on PC Narvik was at 15:45 UTC, 
Saturday, May 09.

Cheers,
David 

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Re: [ntp:questions] How bad is USB?

[David J Taylor]

Hal Murray wrote:
>> I'm in a third category (probably) - as long as my PCs "sound" to
>> have the same time, I'm happy.  Actually, I want UTC as well, but as
>> I have a speaking clock working on two PCs it's "nice" when they
>> both speak at the same time.  I wonder how close that needs to be -
>> a few milliseconds, perhaps?  Here's what I actually get - all with
>> Windows.
>
> The speed of sound in air is 1 ft per millisecond.  So
> a difference of a few ms is only noticable if you are careful
> where you put your ears relative to the speakers.

I know it's off-topic, but how far apart in time does two singers, or 
choir, have to be before you notice?  (No, I'm not suggesting a spoken ref 
clock  ).

David 

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

Folks, I made some tests with various settings for the NMEA driver and the 
results are here:

  http://www.satsignal.eu/ntp/NTP-on-Windows-serial-port.html#usb

Maarten's guess about how to specify the COM port was correct (thanks), 
but setting a port above COM3 failed, so I have created bug report 1183.

Just discovered an "Advanced" button on the Device Manager, Properties, 
Port Settings dialog which /appears/ to let me set COM2, but that's still 
not working with NTP.  Perhaps it's reboot time...

Cheers,
David 

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

Dave Hart wrote:
>> Does NTP even allow COM4?
>
> I don't think so.  The unit numbers are limited to 0-3, I believe, but
> I don't have any concept of why.  Windows never has a COM0:, so
> arguably it was a poor choice to map unit number to com port number
> without adding 1, but it's far too late to change that.  At the cost
> of additional documentation complexity, ntpd could easily enough
> interpret unit 0 as COM4:
>
> Two solutions come to mind, either of which would probably work.
> Somewhere in the registry there lurks a mapping, obviously named by
> someone very young and self-impressed, known as the "COM port
> database".  I got your database right here, buddy.  There's a tiny
> little API used by serial port drivers to claim COM port numbers, but
> I suspect you can ignore the API and fiddle the registry directly.
>
> Quite possibly easiest would be to disable or renumber COM1:, COM2: or
> COM3:.  I think there might even be an easy mousy way to choose the
> COMx: assignment via device manager properties dialogs.  Try changing
> an unused 1-3 to a higher port and your USB adapter will likely claim
> the lowest-numbered available port next boot.
>
> Good luck,
> Dave Hart
>
> P.S.  I predict you'd be able to get better time over the internet
> than over USB, but I'd love to be wrong.   But then, you might end up
> the first to have tried PPS over serial USB and get much better
> results than your predecessors.  Thanks for taking the time to
> investigate this.

Dave,

Thanks for your information.

Checking with the Device Manager, I don't have any COM devices other than 
COM4.  However, if NTP is ever to work over USB/serial, it's essential 
that it handle COM port numbers greeater than 3.  I did see a note about 
COM ports 0..3 in one file, but nothing in the documentation about how to 
set the number.  Any chance of changing it to allow 0..9, for example (I'd 
rather see more than one digit, but I can appreciate that may be a greater 
code change).

I do see an entry:

  HKLM\HARDWARE\DEVICEMAP\SERIALCOMM\Device\VCP0

which is a string "COM4", so perhaps that's what you mean.  I am somewhat 
reluctant to change it as I don't know what it might break!  Oh, and quite 
a few more places as well.  It's an FTDI driver, and I can't find any "how 
to set the port" information on the Internet.  I checked in the device 
manager, and couldn't see a way to re-assign the port number.

COM3 is used by a built-in modem.

Cheers,
David 

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Re: [ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

Maarten Wiltink wrote:
> "David J Taylor"
>  wrote
> in message news:96anl.26389$oo7.7...@text.news.virginmedia.com...
> 
>> Folks,
>> 
>> I've looked through the documents, and I can't see how to set the COM
>> port for the NMEA driver on Windows.  Background: I have a GPS 18 and
>> USB serial converter, and I wanted to see how well that actually
>> performs.  It supplies data on COM4, so I need to tell NTP that's
>> where to look for the serial data, but I can't see a fudge or mode
>> parameter which allows this.
>> 
>> Does NTP even allow COM4?
> 
> By giving it 127.127.x.4 as the reference clock address? (Wild guess.)
> 
> Groetjes,
> Maarten Wiltink

Maarten,

Thanks, I can try   127.127.20.4 (although I note Dave Hart's comments).

Cheers,
David

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[ntp:questions] Setting the COM port for the NMEA driver

[David J Taylor]

Folks,

I've looked through the documents, and I can't see how to set the COM port 
for the NMEA driver on Windows.  Background: I have a GPS 18 and USB 
serial converter, and I wanted to see how well that actually performs.  It 
supplies data on COM4, so I need to tell NTP that's where to look for the 
serial data, but I can't see a fudge or mode parameter which allows this.

Does NTP even allow COM4?

Thanks,
David 

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Re: [ntp:questions] 500ppm - is it too small?

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
[]
>>  http://www.maxim-ic.com/appnotes.cfm/an_pk/3566
>
> This seems to suggest crystals have quadratic temperature dependency.
> My understanding is that normal cuts have cubic dependency.  Of
> course, 32kHz crystals are often cut for wrist watch use, and using a
> cut with quadratic characteristics might give a flatter response
> close to body temperature, at the expense of poorer behaviour for
> signficant deviation.

Ideally, you choose the cut for the application.  Quadratic dependency 
might be good for oven-controlled or on-wrist, but what happens when you 
take the watch off?  Cubic for a wider temperature range, perhaps?

With the cost of computers being as it is, I suspect that every penny 
saved on every component is important.  I'd be interested to know what 
actual accuracies are seen for typical PCs (rather than more expensive 
workstations, minis or mainframes).

Cheers,
David 

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Re: [ntp:questions] 500ppm - is it too small?

[David J Taylor]

David Woolley wrote:
[]
> A reasonable expectation of a cheap crystal is 50ppm static plus
> <10ppm temperature dependent.  When one gets >500ppm it suggests the
> problem is rather worse than poor crystal tolerancing.

I am inclined to agree.  One reference I found was this:

  http://www.maxim-ic.com/appnotes.cfm/an_pk/3566

including the statement about 32KHz crystals:

"There is nothing inherently wrong with using an RTC for timekeeping. 
However, the time will only be as accurate as the reference used. 
Unfortunately, the typical 32.768kHz tuning-fork crystal does not provide 
much accuracy over a wide temperature range. Due to its parabolic nature 
over temperature (Figure 1), this accuracy is typically ±20ppm at room 
temperature (+25°C). This is the equivalent of gaining or losing 1.7 
seconds of time each day, or 10.34 minutes per year. As Figure 1 shows, 
accuracy decreases at more extreme high and low temperatures. The typical 
accuracy at these temperatures is much worse than 150ppm, which is the 
equivalent to losing almost 13.0 seconds of time each day, or over 1.3 
hours per year."

Based on earlier experience, I would expect the higher-frequency crystals 
used for CPU-clock etc. to be rather better than this.

BTW: Windows can keep quite accurate time in some versions, Windows 2000 
and XP for example, however I haven't tamed Vista or Windows-7 as yet. 
It's not as good as FreeBSD, though.

Cheers,
David 

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Re: [ntp:questions] 500ppm - is it too small?

[David J Taylor]

Richard B. Gilbert wrote:
[]
> I'm not here to make people feel good!

No comment!

> I've checked the hardware available to me and none is worse than 50
> PPM. That's two PC's running Windows XP, three Sun Ultra 10
> Workstations running Solaris 8, 9, and 10, two DEC Alpha workstations
> running VMS.

Thanks for that.  Possibly, on the PCs are representative of the hardware 
class I'm considering.

> The specifications for NTPD say that it will correct errors less than
> or equal to 500 PPM.

Hence the title of this thread.

> I beleive that hardware outside of this limit can properly be
> described as broken!  Would *you* tolerate a clock, computer or wall,
> that gained or lost more then 43 seconds per day?  Our forefathers,
> limited to springs, gears and pendulums could do better than that.

As I hope I mentioned earlier, it may not be hardware, but some BIOS or OS 
power-saving scheme, or something else I've overlooked, which is stopping 
NTP from working.  I am trying to get more details.

I do completely agree that a clock with 43s per day error would be one I 
would reject!  All the non-radio and non-NTP clocks here do better than 
that.

Cheers,
David 

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Re: [ntp:questions] 500ppm - is it too small?

[David J Taylor]

Richard B. Gilbert wrote:
[]
> An error greater than 500 PPM suggests seriously broken hardware! There 
> might be some way to "kludge" the software to compensate for
> this brokenness but I think it would be easier and cheaper to fix or
> replace the broken hardware.

I was trying to see what errors might be expected in the typical PC clock 
crystals, but my gut instinct is to agree with you.  However, suggesting 
that someone replace their pride and joy just because it doesn't run ntp 
is unlikely to elicit a favourable response!

Cheers,
David 

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[ntp:questions] 500ppm - is it too small?

[David J Taylor]

I've recent been suggesting the Windows port of NTP as a program suitable 
for an application where the timekeeping needed to be within a second or 
two.  Yes, NTP is overkill, but it has the advantages of multiple servers, 
best server selection, adaptive poll rate, and memory of the clock drift 
etc.  However, on quite a few installations - at a guess between 1% and 
5% - NTP has failed because the click frequency error appears to be too 
great for NTP to correct.

Is there any feeling for changing the 500ppm limit, perhaps to 1000ppm or 
even as much as 5000ppm (to pull a figure out of the hat)?  Or is 500ppm 
generally believed to be the worst error which should be compensated?

One possibility is that some of the problem PCs are portables, with some 
sort of power-saving or even hibernation scheme.  I don't have direct 
visibility of the type of PC.

Thanks,
David 

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Re: [ntp:questions] Window XP - ntp / GMT not working

[David J Taylor]

David Lord wrote:
[]
> On Windows 98 here (GMT) London seems to be BST with an hour
> adjustment for DST so turning off DST is always an hour off UTC.
> I have timezone set as (GMT) Casablanca, Monrovia. :-)
>
> David

That's interesting.  On the Windows-32 systems, London = "GMT" = UTC, and 
having the "Automatically adjust clock for daylight saving changes" 
checked makes the reported time UTC+1 in the summer, and UTC in the 
winter.

Thanks for the heads-up!

David 

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Re: [ntp:questions] Window XP - ntp / GMT not working

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
>> settings.  If you want UTC displayed, just choose a time-zone without
>> any summer-time adjustment, for example:
>>
>>  (GMT) Monrovia, Reykjavik
>>
> But make sure that you continually recheck its status.  Tunisia used
> to be in this class, but had DST at very short notice, last year.

Eek!  Why /do/ people have to play with these things?

Any way, perhaps selecting any GMT, and unchecking "Automatically adjust 
clock for daylight saving changes", may also do what the OP wanted.

Cheers,
David 

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Re: [ntp:questions] Window XP - ntp / GMT not working

[David J Taylor]

randy wilson wrote:
> Hi,
>
> This has to have been solved somewhere but apparently
> my searchfu is not working well.
>
> I have some windows xp computers which we are syncing
> to a time server via ntp. I can see the time server
> has the correct UTC time on it and the the PCs are
> syncing to the server. I have the time zones set to
> GMT on all the PC. The problem is the time is off by
> an hour on all the PCs and I can't figure out why.
>
> Any pointers would be appreciated. I would really like
> to just set the PC clocks to UTC but it does not appear
> XP has that as an option but GMT should be equivalent
> I thought.
>
>
> thx
>
> Randy

Randy,

Windows, like UNIX, works in UTC internally, as does NTP.  There is no 
need to adjust anything for NTP.  Programs can read the UTC time if they 
wish, and use UTC if they need.

Windows displays the time you choose in the Control Panel, Regional 
settings.  If you want UTC displayed, just choose a time-zone without any 
summer-time adjustment, for example:

  (GMT) Monrovia, Reykjavik

If you have the PCs set to:

  (GMT) London, Dublin, Edinburgh, Lisbon

then during the summer, they will display one hour ahead of UTC, just as 
wall-clocks would.

Cheers,
David 

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[ntp:questions] Windows-7 - available for testing NTP

[David J Taylor]

Folks,

I have Windows-7 RC installed on one of my PCs at the moment.  It's 
currently running the VegasV2 version:

  http://www.satsignal.eu/mrtg/hydra_ntp.html

  http://www.satsignal.eu/mrtg/performance_hydra.php

and doing about the same as a Vista PC running similar software, i.e. not 
very well!  I don't know yet how long I will keep that PC running 
Windows-7, but if anyone wants any tests done just ask.

There will be a public beta release of Windows-7 RC tomorrow, so if you 
prefer to test on your own PCs that's going to be easy as well.

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

David Lord wrote:
[]
> I've ntp logs going back many years and for me chrony was better
> suited to handling temperature changes but was originally used
> because of intermittent dialup connection.

Yes, having a history of expected variations due to temperature chnages, 
or perhaps even using the termperature sensors available on the PCs, might 
enable ntp to even better than it does now.

> With ntpd and maxpoll set to a low value (8) I find ntp can
> compensate ok but there is a lot of jitter and offset wanders
> more than I'd like.
>
> With high values of maxpoll (13) I see great stability until
> seasonal or other temperature  changes when ntp seems to lose
> the plot.
>
> This is no more than happens regularly anyway due to asymmetric
> latency in the adsl connection.
>
> I'm expecting a pps source to make a massive difference.

Yes, from milliseconds to microseconds - if you're lucky!

> I'm using NetBSD and just had  one of servers (c3-600)
> disconnected from lan for a while and moved upstairs so I
> could get a less erratic signal from gps/dcf/msf. I need
> external aerials. I'm about 100 mile from Anthorn, 600 mile
> from Frankfurt so suspect some interfering source.
>
> I've previously run NetBSD-1.5 on a 486dlc33, 8MB ram, and will
> try to use one of my junk 486dx6, 20MB ram, as dedicated ntp box,
> if I can get NetBSD-5 to install, otherwise will use one of the
> servers.
>
>
> David

Here in Edinburgh I have several cheap radio-clocks, and they all seem to 
sync OK.  Removing the CRT TVs (4th harmonic of timebase near 60KHz) 
probably helped.  We are less than 120km from Anthorn.  Rather than 
power-up another PC, you will probably find the performance on a shared 
server adequate - depending on your expectations, of course.  You can run 
that serial lead for some distance.

My page describing the hardware is here.  I now have two RS232 outputs 
paralleled from the GPS 18 LVC.
  http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

David Lord wrote:
[]
> cheers
>
> Both those were listed on garmin site as uk suppliers but the RS price
> that came up was almost 170 quid and I couldn't locate the GPS-18x LVC
> on the gpsw site.
>
> I'll check both again anyway in case my eyesight was playing up.

GPS Warehouse have them in stock.

> I had an unreliable Conrad DCF-77 Rx working earlier in the week that
> seemed to be giving around +/- 2ms with just the parse driver. I
> wasn't expecting such good results due to periodic reception problems
> and earlier having had no success at all with a Globalsat br304.
>
>
> David

With the GPS 18 LVC, even with Windows in a non-temperature-controlled 
environment, I'm seeing about +/- 200us (and more plus than minus, it 
seems that each time the heating switches on it generates a positive 
offset spike, but the thermal stabilisation takes much longer and 
generates a more extended negative period).

  http://www.satsignal.eu/mrtg/feenix_ntp_2.html

With FreeBSD on a very old 133MHz Pentium PC, I would easily get within 
20us.

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

David Lord wrote:
[]
> I've had $60  but not accept my cc and require $35 bank transfer
> fee or $60+ +$75 delivery and others don't export so I gave up.
>
> DL

David,

I'm advised that RS Components stock this at GBP 69 + VAT + delivery.  A 
search of their Web site reveals the GPS 18x range:

  
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=gps+18x&x=0&y=0

and this /appears/ to be the LVC version, but it is /not/ completely 
obvious.

  
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=gps+18x+LVC&x=16&y=16

e.g. they say the Garmin part number is 010-00321-36, but that yields 
nothing on a search of the Garmin site.  However, it seems to be correct 
here:

  https://buy.garmin.com/shop/shop.do?pID=27594&pvID=14555#versionTab

These folk in the UK have the unit, at GBP 56.98 + VAT + delivery.

  http://www.gpsw.co.uk/details/prod2402.html

I've bought a GPS 18 LVC from them before, and have just ordered one of 
the newer x-rated units.  The UK total price is about $106  (GBP 71.02).

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

Steve Kostecke wrote:
> On 2009-05-01, David J Taylor  wrote:
>
>> That's the newer 18x version.
>
> The 18x is the replacement for the 18.
>
>> Garmin's web site seems a little confusing - if I try searching the
>> Garmin site for "GPS 18x", all I get is the download for the unit
>> firmware!
>
> There's no need to search.
>
> Just click "Products" on the page top menu and then click "OEM".

.. which shows "GPS 18" and not "GPS 18x", at least from the UK

> Apparently only the USB and PC versions of the older GPS-18 model are
> still available. All three version of the newer GPS-18x model are
> available.

.. and lists: the PC, USB and LVC versions under "Features" but just the 
USB and PC versions under "Versions".  From the OEM link, I'm being pushed 
to the page:

  https://buy.garmin.com/shop/shop.do?cID=158&pID=223

So you can see why it's a little confusing, and I felt the need to search.

I do wish there was somewhere in Europe selling the GPS 18x LVC at a 
reasonable price - it's rather more than the US $80 you quoted.

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

Steve Kostecke wrote:
[]
> The drop-down peoduct selection box on
> https://buy.garmin.com/shop/shop.do?cID=158&pID=27594 lists the
> following versions:
>
> GPS 18x USB - $84.99 USD
> GPS 18x PC  - $84.99 USD
> GPS 18x LVC, 5m - $79.99

That's the newer 18x version.

Garmin's web site seems a little confusing - if I try searching the Garmin 
site for "GPS 18x", all I get is the download for the unit firmware!

I'm sure that the GPS 18x LVC, 5m will be an excellent unit, as it has a 
much better sensitivity than the older GPS 18.

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

Steve Kostecke wrote:
[]
> I was replying to article e-idnzgzia-_i2funz2dnuvz_g9i4...@bresnan.com
> where Nathaniel Homier said:
> 
> "... make matters worse the lvc version has been discontinued."
> 
> The LVC _is_ still available.

It's the "PC" version which is discontinued.

Cheers,
David

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Re: [ntp:questions] How bad is USB?

[David J Taylor]

Richard B. Gilbert wrote:
[]
> You can try it and see what happens!  The results may be sufficiently
> good for your purposes.  You will almost certainly not get microsecond
> accuracy.  If you are willing to settle for +/- 10 milliseconds you
> can almost certainly get that.
>  There are (at least) two groups of people who hang out here:
> a. The "chimeheads" in pursuit of the "one true time", and
> b. The "synchs" who don't really care what time it is as long as all
> their machines have the SAME time.
>
> Both groups use the same tool, NTPD.  It turns out that having a
> stable and accurate source of time makes it much easier to get a
> whole herd of machines to agree on what time it is.

Richard,

Yes, I /could/ try it, but I was rather hoping that someone else already 
had.  I also think that it will be somewhere between 1 microsecond and 10 
milliseconds, but just where?

I'm in a third category (probably) - as long as my PCs "sound" to have the 
same time, I'm happy.  Actually, I want UTC as well, but as I have a 
speaking clock working on two PCs it's "nice" when they both speak at the 
same time.  I wonder how close that needs to be - a few milliseconds, 
perhaps?  Here's what I actually get - all with Windows.

  http://www.satsignal.eu/mrtg/daily_ntp.html

- within about 250 microseconds on my serial/PPS ref-clock PCs
- within about 2 milliseconds on my "Synced from ref-clock" PCs
- within about 25 milliseconds on my Vista PC.

Yes, I used to get better on the ref-clock PCs when running FreeBSD, but 
I've since been able to shut down that PC and just use a Windows box 
instead.  It's good enough for me.

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

E-Mail Sent to this address will be added to the BlackLists wrote:
> Steve Kostecke wrote:
>> The GPS-18 has been replaced by the GPS-18x. According to
>> https://buy.garmin.com/shop/shop.do?cID=158&pID=27594 all
>>  3 varients are still available.
> 
> 4 variants?
> 
> GPS 18x
> Part Number: 010-00321-31 (USB)
> Part Number: 010-00321-34 (PC)
> Part Number: 010-00321-36 (LVC)
> 
> Part Number: 010-00321-37 (5Hz)
> 
> "The GPS 18x 5Hz is a high-sensitivity GPS sensor that
>  replaces the GPS 18 5Hz."

Only GPS 18x LVC and GPS 18x-5Hz have the pulse-per-second (PPS) output.

David

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[ntp:questions] How bad is USB? (was: Re: Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.)

[David J Taylor]

Garrett Wollman wrote:
> In article ,
> Richard B. Gilbert  wrote:
>
>> USB is nearly useless for NTP!  USB has latencies sufficiently large
>> and variable to render it unsuitable for use with NTP.
[]

Garrett, Richard,

You've both commented that USB has drawbacks, but in reality what 
performance might be obtained?  Not everyone needs microsecond precision, 
and USB might allow millisecond precision - i.e. possibly better than what 
might be obtained by Internet access alone, or by using a radio source.

Has anyone made any actual tests or measurements?  Are there any results 
available from an actual installation of USB on either Windows or UNIX?

Thanks,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

E-Mail Sent to this address will be added to the BlackLists wrote:
> David J Taylor wrote:
>> Unruh wrote:
>>> ... RS232 plug and a USB poser plug.
>>
>> Where are you proposing he plug the RS232 lead in?  Buy a PCI/serial
>> card?
>
> Perhaps he meant a USB serial port?

Yes, that's a possibility.  I've not tried one here to know just how much 
extra error is introduced in a typical system.

Cheers,
David 

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Re: [ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

[David J Taylor]

Unruh wrote:
> Nathaniel Homier  writes:
>
>> Hello.
>
>> I would like to know if one can use the line audio out of any old
>> portable shortwave radio tuned to a time signal and fed via a line
>> audio input.  This would be motherboard audio.  The primary reason
>> is that I get the impression that ntp radio clocks are for sale at
>> very high prices.  The most I have to spend is about $200.  I
>> already have very nice Sony 7600G HF portable and that gets the time
>> freq. from 2.5 to 15 very well.  My computer is the new pci express
>> and I have no serial port.
>
> If you have $200, why not get a GPS 18LVC for about $70 and pay your
> local radio hobbyist to install an RS232 plug and a USB poser plug.
> That way you wil get microsecond rather than millisecond accuracy.

Where are you proposing he plug the RS232 lead in?  Buy a PCI/serial card?

David 

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Re: [ntp:questions] making sense of stats offset values [or trying to...]

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
>> David Woolley wrote:
>>> Bruce Lilly wrote:
>> []
>>>># ntpq -p
>>>> remote   refid  st t when poll reach  delay 
>>>> offset  jitter
>>>> *megatron.blilly 18.26.4.105  2 u   27   64  377
>>>> 2.9270.296   0.122
>>>> # ntptrace
>>>> megatron.blilly.net: stratum 2, offset 0.002120, synch
>>>> distance 0.024161
>>>>
>>>>Note that ntpq reports an offset of 0.296 milliseconds from
>>>> the local host to its system peer, while
>>>>ntptrace reports an order of magnitude larger offset!
>>>
>>> 2.120 milli-seconds is not an order of magnitude different.  I think
>>>  you are expecting milliseconds to have three zeros after the
>>> decimal point; they don't!
>>
>> David,
>>
>> I'm missing something here - how are 0.296ms and 2.120ms not about
>> "an order of magnitude different"?
>
> My mistake. I looked at the decimal point on the delay; it wrapped to
> the start of the line.
>
> However, as noted, that is the difference between a one shot
> measurement and a filtered one.

Thanks, David.  I found your explanations most helpful, so thanks for 
those.

Cheers,
David 

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Re: [ntp:questions] making sense of stats offset values [or trying to...]

[David J Taylor]

David Woolley wrote:
> Bruce Lilly wrote:
[]
>># ntpq -p
>> remote   refid  st t when poll reach   delay
>> offset  jitter
>> *megatron.blilly 18.26.4.105  2 u   27   64  377
>> 2.9270.296   0.122
>> # ntptrace
>> megatron.blilly.net: stratum 2, offset 0.002120, synch
>> distance 0.024161
>>
>>Note that ntpq reports an offset of 0.296 milliseconds from
>> the local host to its system peer, while
>>ntptrace reports an order of magnitude larger offset!
>
> 2.120 milli-seconds is not an order of magnitude different.  I think
>  you are expecting milliseconds to have three zeros after the decimal
> point; they don't!

David,

I'm missing something here - how are 0.296ms and 2.120ms not about "an 
order of magnitude different"?

Thanks,
David 

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[ntp:questions] Repost: Are there algorithm differences between 4.2.4 and 4.2.5?

[David J Taylor]

David J Taylor wrote:
> Are there any algorithm of other differences which might cause
> noticeable performance differences between 4.2.4 and 4.2.5?  For
> example: 
> 
> - 4.2.5 being more reluctant to increasing the polling interval from
> 64s (with a mixture of local stratum-1 and Internet pool servers)?
> 
> - 4.2.5 showing an increased variability of offset when viewed on a
> timescale of minutes?
> 
> Of course, these may just be different manifestations of the same
> underlying difference.
> 
> Thanks,
> David

It would be good to hear from the algorithm experts about this topic.

There are some comparative results here:

 http://www.satsignal.eu/ntp/V4.2.4.vs.V4.2.5.html

Thanks,
David

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Re: [ntp:questions] NTP - orphan mode with SAME stratum ("tos orphan 6") FAIL to sync.

[David J Taylor]

sheikdawoodraj...@gmail.com wrote:
[]
> Steve,
> what do you exactly mean "ultra high quality time"?
>
> My ntp service is started running the command below:
> "C:\ntp\bin\ntpd.exe" -U 3 -M -g -c "C:\ntp\etc\ntp.conf"
>
> Are you talking about the -M (Windows only - set high quality
> multimedia timer) option here?

It's one of these "how long is a piece of string" questions!  What 
accuracy do you require?  Within a second, tens of milliseconds, hundreds 
of microseconds?

With Windows XP SP2 or later, the -M option may be required to prevent 
severe variations in the offset value, for example:

  http://www.satsignal.eu/ntp/ntp-events.htm#glitch

By the way, I use MRTG to plot the offsets:

  http://www.satsignal.eu/ntp/NTPandMRTG.html

and the Meinberg NTP Time Server Monitor and a program I wrote can read 
the loopstats files to show how well NTP is working:

  http://www.meinberg.de/english/sw/time-server-monitor.htm

  http://www.satsignal.eu/software/net.htm#NTPplotter

and I have a simple multi-PC monitor here:

  http://www.satsignal.eu/software/net.htm#NTPmonitor

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
>
>> netstat -ano works correctly on my Windows XP Pro SP3.
>>
>
> I ran strings on the Win 98 version to find the help message, so it
> looks like it has changed on XP, although ntpd wouldn't run on 98,
> anyway.

Checked on my Windows 2000 system and the -ano isn't recognised there. 
Probably Windows XP or later.  A lot of the command-line programs and the 
batch language have been substantially enhanced over the years.

Cheers,
David 

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[ntp:questions] Solved - ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

My friend's ISP had an unknown feature - a firewall on the ISP side which 
blocked traffic other than Web and e-mail.  Changing that firewall setting 
from "high" to "low" and restarting his router allowed NTP to work 
correctly and discipline his PC's clock.

Thanks to all the help and suggestions here.

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

David Woolley wrote:
> Danny Mayer wrote:
>>
>> Instead of all that, just run netstat -an from the command line and
>> see if there is anything using 123/UDP port on the local addresses.
>> You can then used netstat -ano to get the PID of the application
>> using that port.
>
> He is running Windows.  There is no -o option on Windows netstat (and
> I'm not sure it is universal on Unix).  PID is also not a familiar
> concept for Windows users, even though there is a corresponding
> concept.

David, Danny,

netstat -ano works correctly on my Windows XP Pro SP3.

PID is easily displayed in Task Manager, Processes tab.  You can use the 
View, Select columns to show the PID.

Thanks for the suggestion, Danny.

Cheers,
David 

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Re: [ntp:questions] NPTdate - difference in packets between -q and not?

[David J Taylor]

Richard B. Gilbert wrote:
> David J Taylor wrote:
>> Richard B. Gilbert wrote:
>> []
>>> NTP passes through my router with no problems.  I never had to do
>>> any configuration to allow it.  It seems to fall under "replies to
>>> outgoing packets are allowed"!  The router is is a LinkSys BEFR81.
>>> YMMV!
>> 
>> Yes, my router also "just works".  We're trying to figure out why
>> someone else's system doesn't.  Thanks, anyway.
>> 
>> Cheers,
>> David
> 
> I have yet to see any mention of the make and model of the router in
> question, configuration, etc, etc.

Linksys model AG241V2 running Firmware V 2.01.03.

David

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Re: [ntp:questions] NPTdate - difference in packets between -q and not?

[David J Taylor]

Richard B. Gilbert wrote:
[]
> NTP passes through my router with no problems.  I never had to do any
> configuration to allow it.  It seems to fall under "replies to
> outgoing packets are allowed"!  The router is is a LinkSys BEFR81.
> YMMV!

Yes, my router also "just works".  We're trying to figure out why someone 
else's system doesn't.  Thanks, anyway.

Cheers,
David 

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Re: [ntp:questions] NPTdate - difference in packets between -q and not?

[David J Taylor]

Richard B. Gilbert wrote:
[]
> Routers sold into the consumer market generally have configuration
> options to allow or block ports and some can be configured to block
> specific IP addresses or address families.  By default they allow
> responses to outgoing packets and block all other incoming traffic.

Thanks, Richard.  I've not met domestic routers which require specific 
configuration for NTP packets, but perhaps I've just been lucky.  Would 
what you describe explain why ntpdate -q  works, but nptdate 
 responds with "no server suitable for synchronization found"?

[By works, I mean he gets a response like:

server 81.171.44.131, stratum 2, offset 12.016615, delay 0.05682
 4 Apr 08:49:58 ntpdate[3936]: step time server 81.171.44.131 offset
12.016615 sec]

Thanks,
David 

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Re: [ntp:questions] NPTdate - difference in packets between -q and not?

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
>
>> What is the difference in the packets sent and received in the two
>> command formats (I appreciate that -q does not set the clock)?
>
> The source port number.  Your friend has a firewall problem.  It is
> blocking replies to port 123.

OK, David.  That's certainly consistent with the other problems we've 
seen.  He claims to be running no software firewall, so perhaps it is 
something in his router?

Would the same apply to ntpq -p?  That also works.

Thanks,
David 

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[ntp:questions] NPTdate - difference in packets between -q and not?

[David J Taylor]

My friend's system shows that ntpdate works with the "-q" ption, but not 
without:

___
E:\NTP\bin>ntpdate -q 81.171.44.131
server 81.171.44.131, stratum 2, offset 12.016615, delay 0.05682
 4 Apr 08:49:58 ntpdate[3936]: step time server 81.171.44.131 offset
12.016615 sec

E:\NTP\bin>ntpdate 81.171.44.131
 4 Apr 08:50:15 ntpdate[5108]: no server suitable for synchronization 
found
___


What is the difference in the packets sent and received in the two command 
formats (I appreciate that -q does not set the clock)?

Thanks,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

Dave Hart wrote:
> On Apr 2, 8:54 am, "David J Taylor"  this-bit.nor-this.co.uk> wrote:
>> Running from the command-line, we get:
>>
>> 2 Apr 09:39:08 ntpd.exe[3984]: frequency initialized 0.000 PPM from
>> e:\NTP\etc\ntp.drift
>> 2 Apr 09:39:22 ntpd.exe[3984]: ntservice: The Network Time Protocol
>> Service has stopped.
>> 2 Apr 09:40:16 ntpd.exe[344]: logging to file log.txt
>> 2 Apr 09:40:16 ntpd.exe[344]: Can't create I/O event handle:
>> Input/output error - another process may be running - EXITING
>> 2 Apr 09:40:16 ntpd.exe[344]: ntservice: The Network Time Protocol
>> Service has stopped.
>
> The Can't create I/O event handle is the error you'll see with
> Meinberg's vegas-v2 when there is another ntpd.exe hanging around.
> Keep in mind the message claiming the service has stopped is a lie, it
> is coming from the service as it is about to stop.  My QPC releases as
> well as official versions starting with 4.2.4p7RC1 and 4.2.5P160 will
> give a differrent error in that case, likely complaining about being
> unable to bind to address 127.0.0.1:123 for example, possibly with a
> different IP address but definitely with port 123.
>
> That doesn't explain why the first process failed, but it does hint it
> is not terminating cleanly after failing.
>
> Martin's suggestion to try a debug binary with tracing enabled is
> probably the next fruitful approach.
>
> Cheers,
> Dave Hart

Thanks, Dave.  I've pointer the user to debug binaries.  I should tell him 
to add a PAUSE after the NET STOP in his batch file.

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

David Lord wrote:
> David J Taylor wrote:
>> David Woolley wrote:
>>> Steve Kostecke wrote:
>>>> On 2009-04-01, David J Taylor 
>>>> wrote:
>>>>> E:\NTP\bin>ntpq -c as
>>>>>
>>>>> ind assID status  conf reach auth condition  last_event cnt
>>>>> ===
>>>>>   1 22554  8000   yes   yes  nonereject
>>>>
>>>> [snip]
>>>>
>>>>> E:\NTP\bin>ntpq -c "rv 22554"
>>>>> assID=22554 status=8000 unreach, conf, no events,
>>>>
>>>> ntpd has not been able to exchange packets with this remote time
>>>> server.
>>>
>>> There is something funny here, as the associations output says it is
>>> reachable (which I why I didn't pick up the unreachable on the rv).
>>
>> Folks, it would be most helpful if you could identify the exact
>> conditions under which this might occur.  I have been trying to trace
>> this "something funny" for days now!
>
> Software/application firewalls sometimes let enough through before
> blocking so that initial connection has appeared successful.
>
>
> David

David, yes firewall was the first thing I thought of, but he says he's 
tried it without.  Will get him to run a more thorough debug version...

Thanks,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

Running from the command-line, we get:

 2 Apr 09:39:08 ntpd.exe[3984]: logging to file log.txt
 2 Apr 09:39:08 ntpd.exe[3984]: precision = 1.000 usec
 2 Apr 09:39:08 ntpd.exe[3984]: Listening on interface #0 wildcard, 
0.0.0.0#123 Disabled
 2 Apr 09:39:08 ntpd.exe[3984]: Listening on interface #1 Loopback 
Interface 1, 127.0.0.1#123 Enabled
 2 Apr 09:39:08 ntpd.exe[3984]: Listening on interface #2 IP Interface 2, 
192.168.1.10#123 Enabled
 2 Apr 09:39:08 ntpd.exe[3984]: frequency initialized 0.000 PPM from 
e:\NTP\etc\ntp.drift
 2 Apr 09:39:22 ntpd.exe[3984]: ntservice: The Network Time Protocol 
Service has stopped.
 2 Apr 09:40:16 ntpd.exe[344]: logging to file log.txt
 2 Apr 09:40:16 ntpd.exe[344]: Can't create I/O event handle: Input/output 
error - another process may be running - EXITING
 2 Apr 09:40:16 ntpd.exe[344]: ntservice: The Network Time Protocol 
Service has stopped.

I don't believe that either ntpd.exe or w32tm.exe is running.

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

David Woolley wrote:
> Steve Kostecke wrote:
>> On 2009-04-01, David J Taylor  wrote:
>>
>>> E:\NTP\bin>ntpq -c as
>>>
>>> ind assID status  conf reach auth condition  last_event cnt
>>> ===
>>>   1 22554  8000   yes   yes  nonereject
>>
>> [snip]
>>
>>> E:\NTP\bin>ntpq -c "rv 22554"
>>> assID=22554 status=8000 unreach, conf, no events,
>>
>> ntpd has not been able to exchange packets with this remote time
>> server.
>
> There is something funny here, as the associations output says it is
> reachable (which I why I didn't pick up the unreachable on the rv).

Folks, it would be most helpful if you could identify the exact conditions 
under which this might occur.  I have been trying to trace this "something 
funny" for days now!

Thanks,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

Richard B. Gilbert wrote:
[]
> Have you tried "ntpd -g"?  That should take care of your offset and
>  give ntpd a chance to maintain the correct time.  Let it run for a
> day or two and try "ntpq -p".  On a "cold" start, ntpd will need at
> least 24 hours to beat your clock into submission.

Thanks, Richard.

I think the -g option is set be default with the Meinberg install.  I 
appreciate that ntpd may take some time to reach ultimate accuracy, but 
ntpq -p usually shows connectivity within minutes.

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

Steve Kostecke wrote:
> On 2009-04-01, David J Taylor  wrote:
>
>> E:\NTP\bin>ntpq -c as
>>
>> ind assID status  conf reach auth condition  last_event cnt
>> ===
>>   1 22554  8000   yes   yes  nonereject
>
> [snip]
>
>> E:\NTP\bin>ntpq -c "rv 22554"
>> assID=22554 status=8000 unreach, conf, no events,
>
> ntpd has not been able to exchange packets with this remote time
> server.
>
>> srcadr=eu1.develooper.com, srcport=123, dstadr=192.168.1.10,
>> dstport=123, leap=11, stratum=16, precision=-20, rootdelay=0.000,
>> rootdispersion=0.000, refid=INIT, reach=000,
>
> It's unreachable.
>
>> I feel that leave me where I started - ntpq -p  works, but
>> ntpd does not.  Oh, and that ntpd thinks it is sending packets...
>
> Take a look for NTP packets with tcpdump.

Steve,

Thanks for that - it's what I had already thought.  I'll get ntpd run from 
the command-line to see if it works that way before bringing in the big 
guns!

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

David Woolley wrote:
> David J Taylor wrote:
>
>> dstport=123, leap=11, stratum=16, precision=-20, rootdelay=0.000,
>
>
> The server is unsynchronised.  I don't know how ntpdate worked.
> It doesn't seem to be the one against which you ran ntpdate; that had
> a public address.

Point taken, but running ntpdate -q against one of the pool servers 
produced the same results.  It's exactly the point now that, with this 
system, ntpdate.exe works from the command-line, but ntpd.exe doesn't work 
when run as a service.  I'm going to get the user to try running ntpd.exe 
interactively to see whether it works that way, and then the question is 
what would stop a Windows service from sending and receiving NTP packets.

Thanks for your help so far.

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

David J Taylor wrote:
> Heiko Gerstung wrote:
> []
>> Can you try to run ntpdate -q  on the machine
>> and check if that works? If not, try ntpdate -qu  to use an
>> unprivileged port. You would need to stop the NTP service on that
>> machine first (net stop ntp).
>
> E:\NTP\bin>ntpdate -q 129.215.160.240
> server 129.215.160.240, stratum 3, offset 6.949179, delay 0.05679
> 1 Apr 16:01:27 ntpdate[744]: step time server 129.215.160.240 offset
> 6.949179 sec
>
> E:\NTP\bin>ntpdate -qu 129.215.160.240
> server 129.215.160.240, stratum 3, offset 6.955597, delay 0.05684
> 1 Apr 16:02:15 ntpdate[5612]: step time server 129.215.160.240 offset
> 6.955597 sec
>
> I see that the error is quite large at 6.9 seconds, but I thought that
> ntpd would see that, and step the clock when it is first run?  Both
> the -q and -qu versions worked correctly, I believe.
>
> []
>> It could be helpful to see the output of "ntpq -p" and "ntpq -c rv
>> " where  is the association ID of one of the remote servers.
>> This id can be found out using "ntpq -c as" .. and yes, the event log
>> would be helpful as well.
>>
>> Best Regards,
>>   Heiko
>
> Heiko,
>
> There was an error in the user typing the ntpq -c "rv 12345" as they
> missed off the quotation marks.  I've asked for this information
> again. However, the ntpq -c as worked:
>
> E:\NTP\bin>ntpq -c as
>
> ind assID status  conf reach auth condition  last_event cnt
> ===
>  1 13978  8000   yes   yes  nonereject
>  2 13979  8000   yes   yes  nonereject
>  3 13980  8000   yes   yes  nonereject
>  4 13981  8000   yes   yes  nonereject
>  5 13982  8000   yes   yes  nonereject
>
> I'm guessing that the reject is because of the 7 second error,
> although I'm uncertain about this.  Would I expect to see last event
> as "reachable" rather than blank?
>
> Puzzled of Edinburgh!
>
> Cheers,
> David

... and more info:

E:\NTP\bin>ntpq -c as

ind assID status  conf reach auth condition  last_event cnt
===
  1 22554  8000   yes   yes  nonereject
  2 22555  8000   yes   yes  nonereject
  3 22556  8000   yes   yes  nonereject
  4 22557  8000   yes   yes  nonereject
  5 22558  8000   yes   yes  nonereject

E:\NTP\bin>

I then tried ntpq -c "rv 22554" here's the result of that

E:\NTP\bin>ntpq -c "rv 22554"
assID=22554 status=8000 unreach, conf, no events,
srcadr=eu1.develooper.com, srcport=123, dstadr=192.168.1.10,
dstport=123, leap=11, stratum=16, precision=-20, rootdelay=0.000,
rootdispersion=0.000, refid=INIT, reach=000, unreach=7, hmode=3,
pmode=0, hpoll=6, ppoll=10, flash=00 ok, keyid=0, ttl=0, offset=0.000,
delay=0.000, dispersion=15937.500, jitter=0.000,
reftime=.  Thu, Feb  7 2036  6:28:16.000,
org=.  Thu, Feb  7 2036  6:28:16.000,
rec=.  Thu, Feb  7 2036  6:28:16.000,
xmt=cd7e23f5.f65dc9b7  Wed, Apr  1 2009 18:33:41.962,
filtdelay= 0.000.000.000.000.000.000.00 
0.00,
filtoffset=0.000.000.000.000.000.000.00 
0.00,
filtdisp=   16000.0 16000.0 16000.0 16000.0 16000.0 16000.0 16000.0 
16000.0

___


I feel that leave me where I started - ntpq -p  works, but ntpd 
does not.  Oh, and that ntpd thinks it is sending packets.

Any help welcome.

Thanks,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

Heiko Gerstung wrote:
[]
> Can you try to run ntpdate -q  on the machine and
> check if that works? If not, try ntpdate -qu  to use an
> unprivileged port. You would need to stop the NTP service on that
> machine first (net stop ntp).

E:\NTP\bin>ntpdate -q 129.215.160.240
server 129.215.160.240, stratum 3, offset 6.949179, delay 0.05679
 1 Apr 16:01:27 ntpdate[744]: step time server 129.215.160.240 offset
6.949179 sec

E:\NTP\bin>ntpdate -qu 129.215.160.240
server 129.215.160.240, stratum 3, offset 6.955597, delay 0.05684
 1 Apr 16:02:15 ntpdate[5612]: step time server 129.215.160.240 offset
6.955597 sec

I see that the error is quite large at 6.9 seconds, but I thought that 
ntpd would see that, and step the clock when it is first run?  Both the -q 
and -qu versions worked correctly, I believe.

[]
> It could be helpful to see the output of "ntpq -p" and "ntpq -c rv
> " where  is the association ID of one of the remote servers.
> This id can be found out using "ntpq -c as" .. and yes, the event log
> would be helpful as well.
>
> Best Regards,
>   Heiko

Heiko,

There was an error in the user typing the ntpq -c "rv 12345" as they 
missed off the quotation marks.  I've asked for this information again. 
However, the ntpq -c as worked:

E:\NTP\bin>ntpq -c as

ind assID status  conf reach auth condition  last_event cnt
===
  1 13978  8000   yes   yes  nonereject
  2 13979  8000   yes   yes  nonereject
  3 13980  8000   yes   yes  nonereject
  4 13981  8000   yes   yes  nonereject
  5 13982  8000   yes   yes  nonereject

I'm guessing that the reject is because of the 7 second error, although 
I'm uncertain about this.  Would I expect to see last event as "reachable" 
rather than blank?

Puzzled of Edinburgh!

Cheers,
David 

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Re: [ntp:questions] ntpd service doesn't connect to remote servers on Windows XP

[David J Taylor]

Heiko Gerstung wrote:
> David J Taylor schrieb:
[]
ce between nptq.exe sending and
>> receiving packets, and ntpd.exe working in its normal manner?
>
> No, not really. If ntpq works you can be sure that
> - network communication works, i.e. you have a valid and working
> network route
> - the server is actually up and running and ntpd is running
> - UDP port 123 is not blocked by a firewall

That's rather what I feared!

> Using ntpdate will completely "simulate" a normal ntpd query and since
> it uses the same or similiar sanity checks and selection algorithms,
>  you should be able to reproduce a problem with it.

OK, thanks.

> I assume that the user did not mess around with the config file that
> has been created by the installer. That should rule out problems
> caused by "restrict".
>
> Regards,
>   Heiko

Not as far as I know - this is just a normal end user double-clicking an 
install, and expecting the resulting installation to work first time.  He 
would not dream of adding "restrict" lines.  Every time I've tried the 
Meinberg installation it has worked perfectly, so I am somewhat at a loss 
to know what has failed here.

Thanks,
David 

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