David J Taylor wrote:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid wrote in
message news:%xqgm.126$ym4...@text.news.virginmedia.com...
Unruh wrote in message news:34jgm.50898$ph1.36...@edtnps82...
[]
Note that chrony will give you a factor of 2 or
RedGrittyBrick wrote:
Unruh wrote:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
At source, it's recently been within about 10 microseconds:
Sorry, at 10usec, the distance away of the transmitter must be less than 3
km.
At
David Woolley da...@ex.djwhome.demon.invalid writes:
David Malone wrote:
The Rugby unit was built by Ian Dowse, and is described here:
http://www.maths.tcd.ie/~dwmalone/time/rugby.html
This is a simple AM detector for the slow code (I don't know if the fast
code is still
John Hasler wrote:
Bill Unruh writes:
The bandwidth of whatever marks it has to be pretty narrow, or the
transmitter would interfer with everything around it. Ie, that means a
large time uncertainty.
The 60KHz WWVB signal is synchronously amplitude-modulated at a 1Hz
rate. The exact cycle
Unruh wrote:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
Unruh wrote in message news:iebhm.50125$db2.41...@edtnps83...
[]
MSF?
See:
http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/msf-radio-time-signal
UK
Maarten Wiltink wrote:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:iebhm.50125$db2.41...@edtnps83...
[...]
The problem is that I have no idea what the accuracy of any of those
items is. YOur ISP's timesever may be a stratum 7 getting time from
a bunch of bozos. Or itmay be stratum
Unruh wrote:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
At source, it's recently been within about 10 microseconds:
Sorry, at 10usec, the distance away of the transmitter must be less than 3 km.
At *source*, the distance to the transmitter must
David J Taylor david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid
writes:
Thanks, David, David and Jan. A few milliseconds is what I had expected,
so if you are on a consumer line, what implications does that have for
unruh's comment?
I've been plotting the offset reported by ntpq
Unruh wrote:
John Hasler jhas...@newsguy.com writes:
Bill Unruh writes:
Sorry, at 10usec, the distance away of the transmitter must be less than 3
km.
10usec at the transmitter.
Also your system needs to see the start of the tone to 10usec which
means that the tone would have to be
David Malone wrote:
The Rugby unit was built by Ian Dowse, and is described here:
http://www.maths.tcd.ie/~dwmalone/time/rugby.html
This is a simple AM detector for the slow code (I don't know if the fast
code is still transmitted). It doesn't phase lock onto the carrier.
David Woolley wrote:
David Malone wrote:
The Rugby unit was built by Ian Dowse, and is described here:
http://www.maths.tcd.ie/~dwmalone/time/rugby.html
This is a simple AM detector for the slow code (I don't know if the fast
code is still transmitted). It doesn't phase lock onto
David Woolley wrote in message
news:hcnjt3$bq...@news.eternal-september.org...
[]
This is a simple AM detector for the slow code (I don't know if the fast
code is still transmitted). It doesn't phase lock onto the carrier.
The fast code stopped many years ago. October 1998 according to:
Bill Unruh writes:
The bandwidth of whatever marks it has to be pretty narrow, or the
transmitter would interfer with everything around it. Ie, that means a
large time uncertainty.
The 60KHz WWVB signal is synchronously amplitude-modulated at a 1Hz
rate. The exact cycle on which the amplitude
John Hasler jhas...@newsguy.com writes:
Bill Unruh writes:
The bandwidth of whatever marks it has to be pretty narrow, or the
transmitter would interfer with everything around it. Ie, that means a
large time uncertainty.
The 60KHz WWVB signal is synchronously amplitude-modulated at a 1Hz
Bill Unruh writes:
This is of course all made totally redundant by the GPS time
delivery-- even makes up for the transmission delay. It begins to look
like like Morse code in the days of cell phones. Quaint, but not
really useful.
One could say the same about NTP.
--
John Hasler
Unruh wrote:
John Hasler jhas...@newsguy.com writes:
The 60KHz WWVB signal is synchronously amplitude-modulated at a 1Hz
rate. The exact cycle on which the amplitude changes can be locked in
by a digital phase-locked loop. A VCXO can be phase-locked to the
carrier to within a
Unruh unruh-s...@physics.ubc.ca wrote in message
news:fgmhm.50325$db2.6...@edtnps83...
[]
This is of course all made totally redundant by the GPS time delivery--
even makes up for the transmission delay. It begins to look like like
Morse code in the days of cell phones. Quaint, but not really
Unruh wrote in message news:rl5hm.50089$db2.40...@edtnps83...
[]
As I tried to emphasise, if the round trip is not symmetric, then
neither ntp not
chrony can compensate for that lack of symmetry, and the absolute time
will be
out. If occasionally it has an assymetric round trip, then ntp
David Lord wrote:
How do you get the time difference between your GPS and system
time?
Include the GPS in your ntp.conf, but mark it with noselect on the server
line.
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questions mailing list
questions@lists.ntp.org
David Lord sn...@lordynet.org writes:
Unruh wrote:
David Lord sn...@lordynet.org writes:
David J Taylor wrote:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:qg_gm.50009$db2.46...@edtnps83...
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:iebhm.50125$db2.41...@edtnps83...
[...]
The problem is that I have no idea what the accuracy of any of those
items is. YOur ISP's timesever may be a stratum 7 getting time from
a bunch of bozos. Or itmay be stratum 1 getting its time from a
David J Taylor david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid
writes:
Unruh wrote in message news:iebhm.50125$db2.41...@edtnps83...
[]
MSF?
See:
http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/msf-radio-time-signal
UK 60KHz radio time
Unruh wrote in message news:vcjhm.50153$db2.9...@edtnps83...
[]
UK 60KHz radio time signal.
Ah, OK. Its accuracy is probably not much better than a few msec I
assume.
GPS is a few usec. Since the network gives accuracies of better than a
few ms, MSF
is not a good way of testing the
David J Taylor writes:
UK 60KHz radio time signal.
Bill Unruh writes:
Ah, OK. Its accuracy is probably not much better than a few msec I
assume.
Should be as good as WWVB, which is good to within 100usec. The
propagation delay is highly predictable at 60KHz. These stations can
also can
I wrote:
Should be as good as WWVB, which is good to within 100usec.
But evidently many commercial receivers are only good to a ms or two.
--
John Hasler
jhas...@newsguy.com
Dancing Horse Hill
Elmwood, WI USA
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questions mailing list
I wrote:
Should be as good as WWVB, which is good to within 100usec. The
David Woolley writes:
Most receivers only use the slow code (including the simple hardware
solutions for ntpd).
I'm assuming a real receiver. With the single-chip designs intended for
atomic watches you'll be lucky to
David J Taylor david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid
writes:
Unruh wrote in message news:vcjhm.50153$db2.9...@edtnps83...
[]
UK 60KHz radio time signal.
Ah, OK. Its accuracy is probably not much better than a few msec I
assume.
GPS is a few usec. Since the network
Bill Unruh writes:
Sorry, at 10usec, the distance away of the transmitter must be less than 3 km.
10usec at the transmitter.
Also your system needs to see the start of the tone to 10usec which
means that the tone would have to be about 1MHz which is a bit beyond
audio.
There isn't any tone.
John Hasler jhas...@newsguy.com writes:
Bill Unruh writes:
Sorry, at 10usec, the distance away of the transmitter must be less than 3
km.
10usec at the transmitter.
Also your system needs to see the start of the tone to 10usec which
means that the tone would have to be about 1MHz which is
Unruh wrote:
John Haslerjhas...@newsguy.com writes:
There isn't any tone. It's the UK equivalent of WWVB.
How is the beginning of the second ( an hour) marked?
The bandwidth of whatever marks it has to be pretty narrow, or the transmitter
would interfer with everything around it. Ie, that
Unruh wrote in message news:34jgm.50898$ph1.36...@edtnps82...
[]
Note that chrony will give you a factor of 2 or three improvement over
ntp in the errors, assuming that the roundtrip is equally split on
Linux or BSD.
For those without wide-bandwidth academic connections - those folks on
David J Taylor david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid
writes:
Unruh wrote in message news:34jgm.50898$ph1.36...@edtnps82...
[]
Note that chrony will give you a factor of 2 or three improvement over
ntp in the errors, assuming that the roundtrip is equally split on
Linux
David J Taylor wrote:
Unruh wrote in message news:34jgm.50898$ph1.36...@edtnps82...
[]
Note that chrony will give you a factor of 2 or three improvement over
ntp in the errors, assuming that the roundtrip is equally split on
Linux or BSD.
For those without wide-bandwidth academic
David J Taylor wrote:
For those without wide-bandwidth academic connections - those folks on
cable or ADSL - how good is an equal split round trip assumption?
I calculated this for my case once (3840 kbit/s down and 512 kbit/s up). The
difference in transmission time due only to the different
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid wrote in
message news:%xqgm.126$ym4...@text.news.virginmedia.com...
Unruh wrote in message news:34jgm.50898$ph1.36...@edtnps82...
[]
Note that chrony will give you a factor of 2 or three improvement over
ntp in the
David J Taylor wrote:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid wrote in
message news:%xqgm.126$ym4...@text.news.virginmedia.com...
Unruh wrote in message news:34jgm.50898$ph1.36...@edtnps82...
[]
Note that chrony will give you a factor of 2 or three
Jan Ceuleers wrote:
This is however only the best case, because it assumes that the
uplink is not saturated. If it is, and if you are able to prioritise your
I suspect most severe asymmetry cases actually happen because the
downlink is saturated. That's is exacerbated by the fact that it is
David J Taylor writes:
On consumer-grade circuits the assumption about equal round trip is
unlikely to be valid.
Why would you expect the asymmetry to be worse there than elsewhere?
--
John Hasler
jhas...@newsguy.com
Dancing Horse Hill
Elmwood, WI USA
Unruh unruh-s...@physics.ubc.ca wrote in message
news:qg_gm.50009$db2.46...@edtnps83...
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid wrote in
message
David J Taylor david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid
writes:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:qg_gm.50009$db2.46...@edtnps83...
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
David J Taylor
David J Taylor writes:
On consumer-grade circuits the assumption about equal round trip is
unlikely to be valid.
Why would you expect the asymmetry to be worse there than elsewhere?
--
John Hasler
It's just an impression I had - that consumers get the worst latency and
most overloaded
Unruh wrote in message news:kx%gm.50022$db2.12...@edtnps83...
[]
As I said, chrony does a linear regression on the last n offsets.
[]
Bill,
I think we have seen these remarks about chrony before.
What I was wanting was a yes/no answer (although numbers would be nice) to
the question:
- is
David J Taylor writes:
It's just an impression I had - that consumers get the worst latency
and most overloaded network equipment...
Perhaps, but it doesn't follow that they suffer a great deal of
asymmetry.
...and no direct connection to an ultra-high-speed academic network.
Of course not,
David J Taylor wrote:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:qg_gm.50009$db2.46...@edtnps83...
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid wrote in
message
David Lord sn...@lordynet.org writes:
David J Taylor wrote:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:qg_gm.50009$db2.46...@edtnps83...
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
David J Taylor
David J Taylor david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid
writes:
Unruh wrote in message news:kx%gm.50022$db2.12...@edtnps83...
[]
As I said, chrony does a linear regression on the last n offsets.
[]
Bill,
I think we have seen these remarks about chrony before.
Some have,
Unruh wrote:
David Lord sn...@lordynet.org writes:
David J Taylor wrote:
Unruh unruh-s...@physics.ubc.ca wrote in message
news:qg_gm.50009$db2.46...@edtnps83...
David J Taylor
david-tay...@blueyonder.not-this-bit.nor-this.co.uk.invalid writes:
David J Taylor
Richard B. Gilbert rgilber...@comcast.net writes:
Juyong Do wrote:
Hi,
Does anyone know any survey or paper measuring absolute time accuracy over
NTP? I saw statistics about offsets, RTT, and dispersion but am not sure how
well those parameters reflect or are correlated with absolute
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