Re: [ntp:questions] Local Time NTP Server

[David Woolley]

On 15/09/2020 23:20, William Unruh wrote:

the noun is Coordinate


The noun is Time.  The C* is an adjective, coordinated or coordonné.  It 
appears the abbreviation is not in correct word order for either of 
French or English: 
.




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Re: [ntp:questions] Local Time NTP Server

[William Unruh]

On 2020-09-15, David Taylor  wrote:
> On 14/09/2020 13:45, Rob van der Putten wrote:
>> Hi there
>> 
>> 
>> On 24/08/2020 16:07, William Unruh wrote:
>> 
>> 
>> 
>>> It was renamed because UTC has nothing to do with Greenwich. For
>>> historical reasons, the time at Greenwich is the same as UTC.
>> 
>> They are not perfectly identical. The difference is however less then 
>> one second;
>> GMT is mean solar time.
>> UTC is TAI (atomic time) + leap seconds.
>> 
>> 
>> 
>> 
>> Regards,
>> Rob
>
> Whilst this may be true, in practice people use GMT when they mean UTC.
>
> BTW: GMT is mean solar time /at Greenwich/.
>
> What annoys me is when Raspberry Shake and others refer to "UTC time"!

Why? Repetition? Is PST time also annoying?
Universal Time Coordinate time is not really repetitious anyway, since
the noun is Coordinate. And UTC time means the type of time defined by
UTC-- since there are lots of other types of time one could use--
including decimal time ( 100 sec/min/ 100min/hr, 10hr/day)
>

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Re: [ntp:questions] Local Time NTP Server

[Rob van der Putten]

Hi there


On 24/08/2020 16:07, William Unruh wrote:




It was renamed because UTC has nothing to do with Greenwich. For
historical reasons, the time at Greenwich is the same as UTC.


They are not perfectly identical. The difference is however less then 
one second;

GMT is mean solar time.
UTC is TAI (atomic time) + leap seconds.




Regards,
Rob

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Re: [ntp:questions] Local Time NTP Server

[David Taylor]

On 14/09/2020 13:45, Rob van der Putten wrote:

Hi there


On 24/08/2020 16:07, William Unruh wrote:




It was renamed because UTC has nothing to do with Greenwich. For
historical reasons, the time at Greenwich is the same as UTC.


They are not perfectly identical. The difference is however less then 
one second;

GMT is mean solar time.
UTC is TAI (atomic time) + leap seconds.




Regards,
Rob


Whilst this may be true, in practice people use GMT when they mean UTC.

BTW: GMT is mean solar time /at Greenwich/.

What annoys me is when Raspberry Shake and others refer to "UTC time"!

--
Cheers,
David
Web: http://www.satsignal.eu

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Re: [ntp:questions] Local Time NTP Server

[Uwe Klein]

Am 24.08.2020 um 12:51 schrieb Beth Connell:

Hi, I'm struggling to find any information on where the free NTP
servers are geographically based. In particular, I'm wondering where
Facebook, Google, Microsoft, etc are based within the UK. Just for
curiousity, I'm wondering how this affects any interference to my
location.

Thanks



The traceroute tool should give you an incling about location.
( if route tracing is allowed and the routers names resolve.
   often provider routers have geo identifiers:

Forex:
traceroute to time-a-g.nist.gov (129.6.15.28), 30 hops max, 40 byte 
packets using UDP

 1  zzz.box (182.168.179.1)  0.277 ms   0.345 ms   0.256 ms
 2  p3e9bf135.dip0.t-ipconnect.de (62.155.241.53)  20.464 ms   20.144 
ms   20.726 ms
 3  f-eh1-i.F.DE.NET.DTAG.DE (62.154.18.70)  30.226 ms   29.796 ms 
29.851 ms

 4  * * *
 5  * * *
 6  CenturyLink-level3-NewYork6.Level3.net (4.68.70.50)  119.547 ms 
118.809 ms   118.944 ms
 7  dca-edge-22.inet.qwest.net (67.14.6.142)  119.632 ms   119.404 ms 
 119.341 ms

 8  204.98.157.238 (204.98.157.238)  123.446 ms   122.953 ms   124.012 ms

doesn't work as well as it used to work.

Uwe

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Re: [ntp:questions] Local Time NTP Server

[David Woolley]

On 24/08/2020 18:48, William Unruh wrote:

You need it to be
fixed, eg to the stars.


The stars move, and, in any case, most people want solar time, not 
sidereal time.  Even solar time varies throughout the year.  I think the 
"mean" in GMT refers to the fact that midnight is only true on average.


Sidereal time still needs a reference point on the earth that is in 
earth surface coordinates, not galactic ones.


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Re: [ntp:questions] Local Time NTP Server

[William Unruh]

On 2020-08-24, Jakob Bohm  wrote:
> On 2020-08-24 16:07, William Unruh wrote:
>> On 2020-08-24, Jakob Bohm  wrote:
>>> On 2020-08-24 12:51, Beth Connell wrote:
 Hi,
 I'm struggling to find any information on where the free NTP servers are 
 geographically based. In particular, I'm wondering where Facebook, Google, 
 Microsoft, etc are based within the UK. Just for curiousity, I'm wondering 
 how this affects any interference to my location.

 Thanks

>>>
>>> All NTP time is GMT (now named UTC, after HM government dropped the
>>> ball).  The only geographic factor is the "ping time" to the time
>>> server, the servers that are the most distant (longest ping) are the
>>> GPS and Galileo satellites, that are hundreds or thousands of km from
>>> the receiver, and use their own (non-NTP) protocols to correct for the
>>> delay.
>> 
>> It was renamed because UTC has nothing to do with Greenwich. For
>> historical reasons, the time at Greenwich is the same as UTC.
>> (Note that the prime meridian now runs through a garbage can in a park
>> just south of the Thames rive in London and not along the line marked
>> on the ground in Greenwich. No idea why you believe the govt dropped the
>> ball. Because the location of Greenwich moves (plate techtonics) it
>> would introduce inaccuracies into the definition of time if it were tied
>> to Greenwich. Also, you cannot ping the sattelites.
>
> I used "ping time" as the popular name of the round trip time (as 
> actually measured by NTP implementations), and thus as a somewhat
> vague reference to the equivalant satellite-to-ground time delay.
>
> As for the reference to HM Government, there was a rumor, many years 
> ago, that the budgets cuts caused the relevant time management job to 
> revert to the IERS in Paris, thus loosing Britain the honor of having 
> the time standard refer to the British victory at the Meridian
> conference.

Is Britain really so bereft of self confidence and feelings of self
worth that they have to hang onto symbols of their past (over 100 year
old) glories? Time is universal, owned by the world.
>
> If the Greenwich observatory had still been in full operation, the
> scientists running it would probably have applied the necessary
> corrections for the ground shifting under their instruments,

You simply cannot have a standard which drifts around. You need it to be
fixed, eg to the stars. 
> rather than having the hole place demolished in favor of a symbolic
> line on the ground.  They would also probably have become the time
> setting command center for the Galileo satellites that replaced their
> daily dropping of an actual ball to signal exact meridian noon to
> ships setting their navigation chronometers.

Again, that daily dropping went outi (as a useful device)  almost a hundred 
years ago, once
radio was invented. (In Canada CBC still broadcasts "At the beginning of
the long dash, the time is exactly 10 oclock Pacific Daylight time"-- I,
just 37 min ago, heard it. I assume BBC has the equivalent.)
That  was a lot more accurate than the one second at best reaction time
to the ball dropping. And even GPS with the 10m fuzzing was over a
million times more accurate. And its lattitude is probably a million
times more accurate than chronometric lattitude. Is there anyone on a
ship these days that still knows how to use a sextant?

>
>
>
>>>
>>> Another problem is if the NTP server is one of those that deliberately
>>> return slightly wrong time before and after each leap second to "smooth
>>> out" the leap, some of the companies you mention reportedly do that.

I agree that that "solution" is pretty horrible.

>>>
>>>
>>> Enjoy
>>>
>>> Jakob
>
>
> Enjoy
>
> Jakob

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Re: [ntp:questions] Local Time NTP Server

[Dan Geist]

- On Aug 24, 2020, at 11:46 AM, Jakob Bohm jb-use...@wisemo.com.invalid 
wrote:

> On 2020-08-24 16:07, William Unruh wrote:
>> On 2020-08-24, Jakob Bohm  wrote:
>>> On 2020-08-24 12:51, Beth Connell wrote:
 Hi,
 I'm struggling to find any information on where the free NTP servers are
 geographically based. In particular, I'm wondering where Facebook, Google,
 Microsoft, etc are based within the UK. Just for curiosity, I'm wondering 
 how
 this affects any interference to my location.

 Thanks

>>>
>>> All NTP time is GMT (now named UTC, after HM government dropped the
>>> ball).  The only geographic factor is the "ping time" to the time
>>> server, the servers that are the most distant (longest ping) are the
>>> GPS and Galileo satellites, that are hundreds or thousands of km from
>>> the receiver, and use their own (non-NTP) protocols to correct for the
>>> delay.
>> 
> 
> I used "ping time" as the popular name of the round trip time (as
> actually measured by NTP implementations), and thus as a somewhat
> vague reference to the equivalent satellite-to-ground time delay.

FYI, GNSS satellite to ground delay compensation has very little/anything to do 
with NTP. When a timing GNSS receiver comes online, it trains to each visible 
bird for a period of time (an hour or more, ideally), allowing that signature 
to move through the entire field of sky. This allows the timing algorithm to 
compensate for mild doppler shift as the sources are coming/going (since 
they're not Geo-stationary). Each source is, however, each at fixed (and 
published) orbital elevation. Triangulation allows a receiver to determine its 
relative elevation. Time delay from each source is derived from that and 
normalized. That timestamp (and phase) are provided to downstream electronics, 
including NTP server software.

There are definitely differences in GNSS performance (chipsets, algorithms, 
constellations), but NTP isn't really accurate enough to make many of those 
deltas relevant. As long as the network path between any given NTP source and 
your NTP client is fairly symmetrical and absent of much contention (jitter), 
the time will be quite accurate. Raw network distance/latency isn't even the 
biggest determining factor in its accuracy.

Thanks.
Dan   
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Re: [ntp:questions] Local Time NTP Server

[Jakob Bohm]

On 2020-08-24 16:07, William Unruh wrote:

On 2020-08-24, Jakob Bohm  wrote:

On 2020-08-24 12:51, Beth Connell wrote:

Hi,
I'm struggling to find any information on where the free NTP servers are 
geographically based. In particular, I'm wondering where Facebook, Google, 
Microsoft, etc are based within the UK. Just for curiousity, I'm wondering how 
this affects any interference to my location.

Thanks



All NTP time is GMT (now named UTC, after HM government dropped the
ball).  The only geographic factor is the "ping time" to the time
server, the servers that are the most distant (longest ping) are the
GPS and Galileo satellites, that are hundreds or thousands of km from
the receiver, and use their own (non-NTP) protocols to correct for the
delay.


It was renamed because UTC has nothing to do with Greenwich. For
historical reasons, the time at Greenwich is the same as UTC.
(Note that the prime meridian now runs through a garbage can in a park
just south of the Thames rive in London and not along the line marked
on the ground in Greenwich. No idea why you believe the govt dropped the
ball. Because the location of Greenwich moves (plate techtonics) it
would introduce inaccuracies into the definition of time if it were tied
to Greenwich. Also, you cannot ping the sattelites.


I used "ping time" as the popular name of the round trip time (as 
actually measured by NTP implementations), and thus as a somewhat

vague reference to the equivalant satellite-to-ground time delay.

As for the reference to HM Government, there was a rumor, many years 
ago, that the budgets cuts caused the relevant time management job to 
revert to the IERS in Paris, thus loosing Britain the honor of having 
the time standard refer to the British victory at the Meridian

conference.

If the Greenwich observatory had still been in full operation, the
scientists running it would probably have applied the necessary
corrections for the ground shifting under their instruments,
rather than having the hole place demolished in favor of a symbolic
line on the ground.  They would also probably have become the time
setting command center for the Galileo satellites that replaced their
daily dropping of an actual ball to signal exact meridian noon to
ships setting their navigation chronometers.





Another problem is if the NTP server is one of those that deliberately
return slightly wrong time before and after each leap second to "smooth
out" the leap, some of the companies you mention reportedly do that.


Enjoy

Jakob



Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
This public discussion message is non-binding and may contain errors.
WiseMo - Remote Service Management for PCs, Phones and Embedded

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[ntp:questions] Local Time NTP Server

[Beth Connell]

Hi, 
I'm struggling to find any information on where the free NTP servers are 
geographically based. In particular, I'm wondering where Facebook, Google, 
Microsoft, etc are based within the UK. Just for curiousity, I'm wondering how 
this affects any interference to my location. 

Thanks

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Re: [ntp:questions] Local Time NTP Server

[William Unruh]

On 2020-08-24, Jakob Bohm  wrote:
> On 2020-08-24 12:51, Beth Connell wrote:
>> Hi,
>> I'm struggling to find any information on where the free NTP servers are 
>> geographically based. In particular, I'm wondering where Facebook, Google, 
>> Microsoft, etc are based within the UK. Just for curiousity, I'm wondering 
>> how this affects any interference to my location.
>> 
>> Thanks
>> 
>
> All NTP time is GMT (now named UTC, after HM government dropped the
> ball).  The only geographic factor is the "ping time" to the time
> server, the servers that are the most distant (longest ping) are the
> GPS and Galileo satellites, that are hundreds or thousands of km from
> the receiver, and use their own (non-NTP) protocols to correct for the
> delay.

It was renamed because UTC has nothing to do with Greenwich. For
historical reasons, the time at Greenwich is the same as UTC. 
(Note that the prime meridian now runs through a garbage can in a park
just south of the Thames rive in London and not along the line marked
on the ground in Greenwich. No idea why you believe the govt dropped the
ball. Because the location of Greenwich moves (plate techtonics) it
would introduce inaccuracies into the definition of time if it were tied
to Greenwich. Also, you cannot ping the sattelites. 
>
> Another problem is if the NTP server is one of those that deliberately
> return slightly wrong time before and after each leap second to "smooth
> out" the leap, some of the companies you mention reportedly do that.
>
>
> Enjoy
>
> Jakob

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Re: [ntp:questions] Local Time NTP Server

[William Unruh]

On 2020-08-24, Beth Connell  wrote:
> Hi, 
> I'm struggling to find any information on where the free NTP servers are 
> geographically based. In particular, I'm wondering where Facebook, Google, 
> Microsoft, etc are based within the UK. Just for curiousity, I'm wondering 
> how this affects any interference to my location. 
All are based all over the place. 
No idea what "interference" you are talking about, but I cannot think of
any definition of that word which would make your last sentance make
sense especially with respect to ntp.
iPerhaps if you told us what you are seeing as a problem with your ntp
use, and then people could perhaps suggest ways of solving that problem.


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Re: [ntp:questions] Local Time NTP Server

[Steven Sommars]

Facebook (time.facebook.com) and Google (time.google.com) NTP services use
anycast ( https://en.wikipedia.org/wiki/Anycast ) and have a number of NTP
servers in unpublished locations.  If all goes well NTP requests reach a
nearby server.  There is no guarantee.

Microsoft (time.windows.com) NTP servers use unicast.  The IP addresses and
locations of these servers have varied over time and are unpublished, as
far as I know.

The NTP pool  ( https://www.ntppool.org/en/ ) may help find a nearby NTP
server, but the locations are not guaranteed.

IP pings (ICMP echo request/response) travel from the client to the
terrestrial NTP server, not to the satellites.

On Mon, Aug 24, 2020 at 6:39 AM Jakob Bohm 
wrote:

> On 2020-08-24 12:51, Beth Connell wrote:
> > Hi,
> > I'm struggling to find any information on where the free NTP servers are
> geographically based. In particular, I'm wondering where Facebook, Google,
> Microsoft, etc are based within the UK. Just for curiousity, I'm wondering
> how this affects any interference to my location.
> >
> > Thanks
> >
>
> All NTP time is GMT (now named UTC, after HM government dropped the
> ball).  The only geographic factor is the "ping time" to the time
> server, the servers that are the most distant (longest ping) are the
> GPS and Galileo satellites, that are hundreds or thousands of km from
> the receiver, and use their own (non-NTP) protocols to correct for the
> delay.
>
> Another problem is if the NTP server is one of those that deliberately
> return slightly wrong time before and after each leap second to "smooth
> out" the leap, some of the companies you mention reportedly do that.
>
>
> Enjoy
>
> Jakob
> --
> Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
> Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
> This public discussion message is non-binding and may contain errors.
> WiseMo - Remote Service Management for PCs, Phones and Embedded
>
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Re: [ntp:questions] Local Time NTP Server

[Jakob Bohm]

On 2020-08-24 12:51, Beth Connell wrote:

Hi,
I'm struggling to find any information on where the free NTP servers are 
geographically based. In particular, I'm wondering where Facebook, Google, 
Microsoft, etc are based within the UK. Just for curiousity, I'm wondering how 
this affects any interference to my location.

Thanks



All NTP time is GMT (now named UTC, after HM government dropped the
ball).  The only geographic factor is the "ping time" to the time
server, the servers that are the most distant (longest ping) are the
GPS and Galileo satellites, that are hundreds or thousands of km from
the receiver, and use their own (non-NTP) protocols to correct for the
delay.

Another problem is if the NTP server is one of those that deliberately
return slightly wrong time before and after each leap second to "smooth
out" the leap, some of the companies you mention reportedly do that.


Enjoy

Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S.  https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark.  Direct +45 31 13 16 10
This public discussion message is non-binding and may contain errors.
WiseMo - Remote Service Management for PCs, Phones and Embedded

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