Terje Mathisen wrote:
If you have ethernet cards that support hw time sync
(I don't remember the spec number),
1588 ?
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Paul Sobey wrote:
Some of these sites vary in their willingness to allow
GPS antenas on roofs as well, joy.
If timing is more important than money, you could always get
a rubidium / cesium, frequency / time reference {e.g. Symmetricom},
if the office politics and/or the physical layout of
On 2012-01-04, E-Mail Sent to this address will be added to the BlackLists
Null@BlackList.Anitech-Systems.invalid wrote:
Paul Sobey wrote:
Some of these sites vary in their willingness to allow
GPS antenas on roofs as well, joy.
roof? roof is not necessarily necessary. -- Try a window facing
On 12/29/2011 8:38 PM, Dennis Ferguson wrote:
On 29 Dec, 2011, at 23:26 , Terje Mathisen wrote:
Danny Mayer wrote:
No, they use synchronized Cesium atomic clocks for time accuracy. GPS is
only used to get a fix on the location and I'm not sure that 10's of
centimeters is good enough for
Danny Mayer ma...@ntp.org wrote:
On 12/29/2011 8:38 PM, Dennis Ferguson wrote:
On 29 Dec, 2011, at 23:26 , Terje Mathisen wrote:
Danny Mayer wrote:
No, they use synchronized Cesium atomic clocks for time accuracy. GPS is
only used to get a fix on the location and I'm not sure that 10's of
Danny Mayer wrote:
No, they use synchronized Cesium atomic clocks for time accuracy. GPS is
only used to get a fix on the location and I'm not sure that 10's of
centimeters is good enough for what they are trying to prove. I'd have
to look closely at the methods used and the data to even have a
People really do need to read the paper rather then guess.
Yes, As some have said, normally GPS is not accurate enough for this
level of work but they are not using GPS in the normal way. What they
do is agree on ONE specific GPS satellite that happens to be visible
at both locations. Each site
On 29 Dec, 2011, at 23:26 , Terje Mathisen wrote:
Danny Mayer wrote:
No, they use synchronized Cesium atomic clocks for time accuracy. GPS is
only used to get a fix on the location and I'm not sure that 10's of
centimeters is good enough for what they are trying to prove. I'd have
to look
On 12/27/2011 11:45 PM, Greg Hennessy wrote:
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 9:08 PM, John Hasler wrote:
Danny writes:
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
The requirement is for
On 12/28/2011 12:09 AM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 8:48 PM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky
On 12/28/2011 12:17 AM, unruh wrote:
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
No they do not. They use GPS.
The experiment between Cern and San Grasso for superluminal neutrinos
uses atomic clocks which are synchrononized with GPS.
Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 11:45 PM, Greg Hennessy wrote:
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 9:08 PM, John Hasler wrote:
Danny writes:
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
Danny Mayer ma...@ntp.org wrote:
On 12/28/2011 12:09 AM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 8:48 PM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler
Danny Mayer ma...@ntp.org wrote:
On 12/28/2011 12:17 AM, unruh wrote:
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Message-
From: questions-bounces+elliott.ch=verizon@lists.ntp.org
[mailto:questions-bounces+elliott.ch=verizon@lists.ntp.org] On
Behalf Of Danny Mayer
Sent: Tuesday, December 27, 2011 11:36 PM
To: Greg Hennessy
Cc: questions@lists.ntp.org
Subject: Re: [ntp:questions] Accuracy of NTP
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 11:45 PM, Greg Hennessy wrote:
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 9:08 PM, John Hasler wrote:
Danny writes:
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/28/2011 12:17 AM, unruh wrote:
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/28/2011 12:09 AM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 8:48 PM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John
Danny Mayer wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
The bottom line is that the only thing that is relevant is how easy it is
to get to a GPS antenna with an open view of the sky.
Everything else is bloviation.
GPS is not used for this kind of thing, they are too
On 12/24/2011 1:11 PM, unruh wrote:
On 2011-12-24, John Hasler jhas...@newsguy.com wrote:
I wrote:
An upcoming experiment at Fermilab will observe neutrinos at both ends
(the far end will be in Minnesota).
unruh writes:
Well, no. At best the electrons or muons at one end.
At best the
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is horizontally down the tunnel to
the entrance which is next
Danny writes:
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
The requirement is for synchronization. They use common view GPS.
--
John Hasler
jhas...@newsguy.com
Dancing Horse Hill
Elmwood, WI USA
Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is horizontally down the
On 12/27/2011 8:48 PM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the
On 12/27/2011 9:08 PM, John Hasler wrote:
Danny writes:
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
The requirement is for synchronization. They use common view GPS.
That's not good enough for experiments like this.
Danny
The bottom line is that the only thing that is relevant is how easy it is
to get to a GPS antenna with an open view of the sky.
Everything else is bloviation.
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
GPS is indeed used
At 10:40 PM 12/27/2011, Danny Mayer wrote...
On 12/27/2011 9:08 PM, John Hasler wrote:
The requirement is for synchronization. They use common view GPS.
That's not good enough for experiments like this.
You say that as if it's a fact. You're on the wrong list to just make
such an
On 12/27/2011 10:39 PM, Greg Hennessy wrote:
The bottom line is that the only thing that is relevant is how easy it is
to get to a GPS antenna with an open view of the sky.
Everything else is bloviation.
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter.
Greg Hennessy greg.henne...@cox.net wrote:
The bottom line is that the only thing that is relevant is how easy it is
to get to a GPS antenna with an open view of the sky.
Everything else is bloviation.
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter.
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 9:08 PM, John Hasler wrote:
Danny writes:
GPS is not used for this kind of thing, they are too inaccurate, so it
doesn't matter. They use atomic clocks.
The requirement is for synchronization. They use common view GPS.
That's
On 2011-12-28, Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is horizontally
Danny Mayer ma...@ntp.org wrote:
On 12/27/2011 8:48 PM, j...@specsol.spam.sux.com wrote:
Danny Mayer ma...@ntp.org wrote:
On 12/24/2011 8:10 PM, j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
Again, were do you see the word few in what I wrote?
That makes the statement so meaningless. Every distance can be
measured in feet.
Of couse, nobody at Cern would even think of doing that, but that is
another matter.
On 12/25/2011 5:49 AM, Rob wrote:
j...@specsol.spam.sux.comj...@specsol.spam.sux.com wrote:
Again, were do you see the word few in what I wrote?
That makes the statement so meaningless. Every distance can be
measured in feet.
Of couse, nobody at Cern would even think of doing that, but
Rob nom...@example.com wrote:
j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
Again, were do you see the word few in what I wrote?
That makes the statement so meaningless. Every distance can be
measured in feet.
If I had written exactly the same thing with the exception of using
I wrote:
An upcoming experiment at Fermilab will observe neutrinos at both ends
(the far end will be in Minnesota).
unruh writes:
Well, no. At best the electrons or muons at one end.
At best the electrical pulse produced by a photomultiplier when struck
by a photon generated when a muon or
On 2011-12-24, John Hasler jhas...@newsguy.com wrote:
I wrote:
An upcoming experiment at Fermilab will observe neutrinos at both ends
(the far end will be in Minnesota).
unruh writes:
Well, no. At best the electrons or muons at one end.
At best the electrical pulse produced by a
unruh writes:
They require ns accuracy in the timing and m accuracy in the
distance. And the timing is not simply gps ( although they could have
gotten that wrong) but then that timing has to be brought down into
the mine a km or so below ground and horizontally and that also has to
be
John Hasler jhas...@newsguy.com wrote:
unruh writes:
They require ns accuracy in the timing and m accuracy in the
distance. And the timing is not simply gps ( although they could have
gotten that wrong) but then that timing has to be brought down into
the mine a km or so below ground and
On 2011-12-24, j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
unruh writes:
They require ns accuracy in the timing and m accuracy in the
distance. And the timing is not simply gps ( although they could have
gotten that wrong) but then that
On 2011-12-24, John Hasler jhas...@newsguy.com wrote:
unruh writes:
They require ns accuracy in the timing and m accuracy in the
distance. And the timing is not simply gps ( although they could have
gotten that wrong) but then that timing has to be brought down into
the mine a km or so below
unruh un...@invalid.ca wrote:
On 2011-12-24, j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
unruh writes:
They require ns accuracy in the timing and m accuracy in the
distance. And the timing is not simply gps ( although they could have
unruh writes:
Surveying is done by GPS, as is timing so mountain ranges do not
really matter.
The OPERA team had to survey a traverse through the Gran Sasso highway
tunnel to get to suitable benchmarks. You're right though: they did not
survey the entire distance.
--
John Hasler
Jim Pennino writes:
The issue is that most people don't seem to be able to understand how
to get an accurate position of a location that is vertically under a
km or so of dirt, yet horizontally feet from wide open sky and GPS
signals.
The open sky nearest the OPERA detector is straight up
John Hasler jhas...@newsguy.com wrote:
Jim Pennino writes:
The issue is that most people don't seem to be able to understand how
to get an accurate position of a location that is vertically under a
km or so of dirt, yet horizontally feet from wide open sky and GPS
signals.
The open sky
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is horizontally down the tunnel to
the entrance which is next to a freeway.
Yes, the entrance is next to a freeway. The entrance to the LNGS
facility where
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is horizontally down the tunnel to
the entrance which is next to a freeway.
Yes, the entrance is next to a freeway.
unruh un...@invalid.ca wrote:
On 2011-12-24, j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
unruh un...@invalid.ca wrote:
On 2011-12-24, j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
unruh writes:
They require ns accuracy in the
On 2011-12-25, j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is horizontally down the tunnel to
the
unruh un...@invalid.ca wrote:
On 2011-12-25, j...@specsol.spam.sux.com j...@specsol.spam.sux.com wrote:
John Hasler jhas...@newsguy.com wrote:
The open sky nearest the OPERA detector is straight up through 1400m of
rock.
Jim Pennino writes:
And the easiest open sky to get to is
Richard B. Gilbert wrote:
On 12/22/2011 9:17 PM, Chris Adams wrote:
The securities traders (especially HFT) want it. I suspect the OP is in
that group. That level of timekeeping has been discussed here before.
I think that the radio astronomers are some of the most demanding.
They need far
Paul Sobey wrote:
Our internal testing to this point is that a stock ntpd pointed against
a stratum 1 clock on a low contention gigabit ethernet (stratum 1 source
and client less than 1ms apart) reports its own accuracy at approx 200
microseconds. Further tuning the ntp config by adding the
Paul Sobey wrote:
Our internal testing to this point is that a stock ntpd pointed against
a stratum 1 clock on a low contention gigabit ethernet (stratum 1 source
and client less than 1ms apart) reports its own accuracy at approx 200
microseconds. Further tuning the ntp config by adding the
I hear from many vendors and industry colleagues that 'ntp just isn't
suitable for high precision work and anything less than 1-2ms precision
requires ptp or direct connection to gps clock'. I find these numbers
For microsecond accuracy, I would say that NTP needs direct (PPS) connection
What OS are your hosts running? If it's Windows, millisecond, not
microsecond accuracy will be what you can get at best when syncing over the
network.
A mixture of linux flavours and solaris. For the linux hosts I have a
little more control over which version of ntpd I deploy. For the
What OS are your hosts running? If it's Windows, millisecond, not
microsecond accuracy will be what you can get at best when syncing over
the network.
A mixture of linux flavours and solaris. For the linux hosts I have a
little more control over which version of ntpd I deploy. For the
On 2011-12-23, Paul Sobey bud...@the-annexe.net wrote:
I hear from many vendors and industry colleagues that 'ntp just isn't
suitable for high precision work and anything less than 1-2ms precision
requires ptp or direct connection to gps clock'. I find these numbers
For microsecond
Paul Sobey wrote:
Gbit and low jitter is not quite compatible: 100 Mbit switches were
using cut-through, while (afaik) all Gbit and up switches use store
forward, leading to higher latency and jitter.
There are several varieties of cut-through gig/10GB switch available now
- but noting that
On Fri, Dec 23, 2011 at 17:02, Terje Mathisen terje.mathisen at
tmsw.no@ntp.org wrote:
A fast system time query will load the time as of the last hw clock tick,
along with the corresponding RDTSC (or similar, constant-rate highres clock
source), load the current RDTSC value, then re-read the OS
I see a common misconception here. Most of the concepts about NTP
can be explained using a common wristwatch.
One is that more frequent checking to a standard keeps the time closer
to the standard. That would be true only if you set your watch to
match the standard each time. NTP does not do
On Fri, Dec 23, 2011 at 2:09 AM, Terje Mathisen terje.mathisen at
tmsw.no@ntp.org wrote:
The best (and probably only possible) solution that does give you
single-digit us is to route a PPS signal to each and every server, then use
the network for approximate (~100 us) timing, with the PPS
On 12/22/2011 11:35 PM, unruh wrote:
On 2011-12-23, Richard B. Gilbertrgilber...@comcast.net wrote:
On 12/22/2011 2:11 PM, Paul Sobey wrote:
Dear All,
I work for a firm which requires clocks to be synchronised to quite a
high degree of accuracy.
We have an existing ntp-based infrastructure
: [ntp:questions] Accuracy of NTP - Advice Needed
Our problem will be that running coax around many sites to lots of machines,
many of which don't have serial ports (think blades), is both highly time
consuming and maintenance intensive. If we have to do it then we will but I'd
like a clear idea
Richard B. Gilbert wrote:
How do you tag a neutrino so that you can say with assurance that the
the neutrino that left Cern is the same neutrino that arrives at Sasso?
Jim Pennino writes:
By sending them in a pulse of a known width.
It should be noted, however, that you cannot observe the
John Hasler jhas...@newsguy.com wrote:
Richard B. Gilbert wrote:
How do you tag a neutrino so that you can say with assurance that the
the neutrino that left Cern is the same neutrino that arrives at Sasso?
Jim Pennino writes:
By sending them in a pulse of a known width.
It should be
At 01:58 PM 12/23/2011, Chris Albertson wrote...
But there is no hop of doing uS
level over the gigabit either net.
IEEE 1588.
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On 2011-12-23, John Hasler jhas...@newsguy.com wrote:
An
upcoming experiment at Fermilab will observe neutrinos at both ends (the
far end will be in Minnesota).
But not the same neutrino, since you can only detect the neutrino
after it has collided with something else.
On Fri, Dec 23, 2011 at 5:51 PM, Mike S mi...@flatsurface.com wrote:
At 01:58 PM 12/23/2011, Chris Albertson wrote...
But there is no hop of doing uS
level over the gigabit either net.
IEEE 1588.
Seem 1588 can work at the sub uS level but actual real-work software
on Linux works at the
On 2011-12-23, John Hasler jhas...@newsguy.com wrote:
Richard B. Gilbert wrote:
How do you tag a neutrino so that you can say with assurance that the
the neutrino that left Cern is the same neutrino that arrives at Sasso?
Jim Pennino writes:
By sending them in a pulse of a known width.
It
On 2011-12-23, Richard B. Gilbert rgilber...@comcast.net wrote:
On 12/22/2011 11:35 PM, unruh wrote:
On 2011-12-23, Richard B. Gilbertrgilber...@comcast.net wrote:
On 12/22/2011 2:11 PM, Paul Sobey wrote:
Dear All,
I work for a firm which requires clocks to be synchronised to quite a
high
On 23 Dec, 2011, at 22:47 , Paul Sobey wrote:
I appreciate these may appear to be silly questions with obvious answers
- I am grateful in advance for your patience, and any research sources
you may direct me to.
The best (and probably only possible) solution that does give you
On 2011-12-24, Chris Albertson albertson.ch...@gmail.com wrote:
On Fri, Dec 23, 2011 at 5:51 PM, Mike S mi...@flatsurface.com wrote:
At 01:58 PM 12/23/2011, Chris Albertson wrote...
But there is no hop of doing uS
level over the gigabit either net.
IEEE 1588.
Seem 1588 can work at the
On Fri, Dec 23, 2011 at 10:06 PM, unruh un...@invalid.ca wrote:
If you really go to stamping the interrupt directly as it comes in on
the kernel level, rather
than waiting for a driver (eg the serial driver) to report that the
itnerrupt has occured to userland, you can get it down to 1-2us.
On 12/22/2011 2:11 PM, Paul Sobey wrote:
Dear All,
I work for a firm which requires clocks to be synchronised to quite a
high degree of accuracy.
We have an existing ntp-based infrastructure but want to improve on it
to the point where the bulk of our hosts are synchronised to single
digit
Once upon a time, Richard B. Gilbert rgilber...@comcast.net said:
The last time I heard, there were twenty-seven GPS satellites in
service.
There are currently 31 active.
There are usually anywhere from three to five or six above the
horizon at any given time.
It can be up to 8 or 9.
This
On 12/22/2011 9:17 PM, Chris Adams wrote:
Once upon a time, Richard B. Gilbertrgilber...@comcast.net said:
The last time I heard, there were twenty-seven GPS satellites in
service.
There are currently 31 active.
There are usually anywhere from three to five or six above the
horizon at any
On Thu, Dec 22, 2011 at 19:11, Paul Sobey bud...@the-annexe.net wrote:
- can ntpd's own reported offset (ntpq -p or loopstats) be trusted
(assuming high priority means it gets scheduled as desired)? I've quoted
our apparent numbers at several people and the response is always 'pfft
you
On 2011-12-22, Paul Sobey bud...@the-annexe.net wrote:
Dear All,
I work for a firm which requires clocks to be synchronised to quite a high
degree of accuracy.
What does quite a high degree of accuracy mean? Nearst hour, minute,
second, millisecond, microsecond, nanosecond, picosecond,...?
On Friday 23 December 2011 03:25:18 Dave Hart wrote:
On Thu, Dec 22, 2011 at 19:11, Paul Sobey bud...@the-annexe.net wrote:
- can ntpd's own reported offset (ntpq -p or loopstats) be trusted
(assuming high priority means it gets scheduled as desired)? I've
quoted
our apparent numbers at
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