Problem with Linux Machine's Request for Time from an XP Machine

Allen McIntosh <nospam@mouse-potato.com> wrote:
>Floyd L. Davidson wrote:
>> If you
>> want to see what is involved, here is a very good description:
>> http://www.wraith.sf.ca.us/ntp/
>
>Since you brought it up, let me just mention the fine print for
>the record. I use a GPS 35 to keep my machine at home in sync
>(side effect of some network measurement work). It seems to
>need to "see" a good chunk of the sky in order to work well. It
>took a bit of experimentation to get it placed just right. A
>house at the bottom of the north side of a hill might be
>problematic.

Allen brings up a significant point, both in terms of how such
equipment is implemented in commercial use (where the required
reliability means redundancy is essential) and as a direction to
look toward future developments of inexpensive time and
frequency standards.

Commercial implementations commonly use two Stratum 2 level
clocks (typically rubidium based) synchronized by GPS to Stratum
1 level accuracy. That arrangement can tolerate failure of the
GPS or one of the Stratum 2 clocks and still provide sufficient
accuracy for at least one month.

Note that the definition of "stratum" levels is different than
seen when discussing NTP. A Stratum 1 clock is defined by ANSI
to have a minimum accuracy of +/- 1x10e11 over 20 year period.
A Stratum 1 level clock is capable of standalone operation
(plesiochronous synchronization) and does not require
synchronization for accuracy, therefore no minimum stability is
specified for a Stratum 1 clock.

Stratum 2 is defined as having minimum accuracy of +/- 1.6x10e8
and minimum stability is a drift rate of less than +/- 1x10e10
per day, with the capability of being synchronized to a clock
with the same accuracy. (Stratum 3 and 4 clocks are also
defined, but have either very short term or no holdover
accuracy, and require synchronization to maintain accuracy
better than +/- 4.6x10e6.)

Typically a cesium clock has +/- 1x10e11 accuracy, and a GPS
synchronized clock can reach +/- 1x10e12. Historically, Stratum
1 clocks were expensive until the recent advent of GPS
synchronized units.

Prior to GPS, typically Stratum 2 clocks were synchronized
either from a timing source clocked by a Statrum 1 clock (T1
carrier facilities) or from Loran C (similar to using GPS). GPS
has the advantage of being available almost anywhere, and since
it has become ubiquitous it has also become inexpensive.

GPS has disadvantages too, which appear to be overcome by a
recently developed miniature cesium based clock. GPS, as noted,
requires satellite communications, which is simply not available
inside buildings or behind mountains. GPS is also not small
enough to fit into an individual cell phone. But DARPA and NIST
have recently developed a cesium clock, with 1x10e11 accuracy,
that is the size of a grain of rice and is expected to initially
cost less than $200.

For hobbiest the results may be two fold. First, the cost of
these cesium clocks will probably soon be within range of the
more dedicated (I'm hoping to see a PCI board with a cesium
based clock available with a year or two for less than $300.)
Second, as commercial companies replace older time and frequency
standards with newer equipment there should be a flood of very
interesting used equipment with rock bottom prices.

Relatively soon we'll all have what Allen has!

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@barrow.com

Floyd L. Davidson wrote:

> Prior to GPS, typically Stratum 2 clocks were synchronized
> either from a timing source clocked by a Statrum 1 clock (T1
> carrier facilities) or from Loran C (similar to using GPS).**GPS
> has the advantage of being available almost anywhere, and since
> it has become ubiquitous it has also become inexpensive.
>

In the communications company I used to work for, we had Loran derived
clocks, made by Austron, to provide timing for the DS1 (the correct term
for what is commonly called T1), DS3 and SONET systems.

Incidentally, I recall an interesting discussion I once had with one of the
techs. I pointed out that the office clock was wrong and he insisted it
was correct, as it used the network clock as a time base. What he missed,
was that while the time base was extremely accurate, the clock itself was
simply set to the wrong time and was consistantly wrong by precisely the
same amount. ;-)

Floyd L. Davidson wrote:

> But*DARPA*and*NIST
> have recently developed a cesium clock, with 1x10e11 accuracy,
> that is the size of a grain of rice and is expected to initially
> cost less than $200.

Hmmm... That could be used in a wrist watch. Imagine, a stratum 1 clock on
your wrist!

On Fri, 14 Jan 2005 18:29:44 -0500, James Knott wrote:

> Floyd L. Davidson wrote:
>
>> But*DARPA*and*NIST
>> have recently developed a cesium clock, with 1x10e11 accuracy,
>> that is the size of a grain of rice and is expected to initially
>> cost less than $200.
>
> Hmmm... That could be used in a wrist watch. Imagine, a stratum 1 clock on
> your wrist!

It's hard to read the time accurately off something the size of a grain of
rice ;-)

--
Mark South: World Citizen, Net Denizen

James Knott <james.knott@rogers.com> wrote:
>Floyd L. Davidson wrote:
>
>> Prior to GPS, typically Stratum 2 clocks were synchronized
>> either from a timing source clocked by a Statrum 1 clock (T1
>> carrier facilities) or from Loran C (similar to using GPS).**GPS
>> has the advantage of being available almost anywhere, and since
>> it has become ubiquitous it has also become inexpensive.
>>
>
>In the communications company I used to work for, we had Loran derived
>clocks, made by Austron, to provide timing for the DS1 (the correct term
>for what is commonly called T1), DS3 and SONET systems.

Technically a T1 and a DS1 are two different things, though most
people tend to use them interchangeably to mean either of them.
DS1 is the interface. T1 is a carrier system (probably with a
DS1 interface).

I don't generally make much of a big deal about the difference,
and in the above instance it would have been perhaps more
correct to say DS1 than T1, though not all DS1s are suitable for
timing, while all T1s are.

>Incidentally, I recall an interesting discussion I once had with one of the
>techs. I pointed out that the office clock was wrong and he insisted it
>was correct, as it used the network clock as a time base. What he missed,
>was that while the time base was extremely accurate, the clock itself was
>simply set to the wrong time and was consistantly wrong by precisely the
>same amount. ;-)

That's the problem seen in the web page that was presented as a
method for the OP to run a time server on XP. It listed
precision at well within the specs necessary, but the *accuracy*
was way too far out of bounds.

In regard to Loran-C timing systems, I had an interesting
experience once. We had one installed in the early 80's, and in
the wonderful (i.e., fitting for a Dilbert cartoon) perception
of management, exactly one technician was sent to maintenance
school. So a dozen years go by... and one day it fails. This
thing is located at the back of the equipment room. I just
happen to be standing in the one position where I can look all
the way down an aisle and see the _front_ door at the other end
of the building. At just the point where the Pointy Hair Boss
(who literally did look almost exactly like Dilbert's PHB) says
"Who was it we sent to school on this thing???", I see that
particular individual heading out the front door about as fast
as he can escape. I just about died laughing, because it seemed
also that I was the only one who actually remembered who it was
that had been sent to school.

(Now, in all honesty, I must admit... the tech did *not* even
know that the Loran-C system had failed, and was not running
away from a nasty job. If he had known, he probably would have
been moving twice as fast. The fact is he had something like a
doctor's appointment... But of course we didn't know that until
hours later. Regardless, I didn't say a word until after he'd
had enough time to escape. The point, in my mind, was that
having only one person schooled on something that critical was
poor planning.)

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@barrow.com

Mark South <marksouth@null.invalid> wrote:
>On Fri, 14 Jan 2005 18:29:44 -0500, James Knott wrote:
>
>> Floyd L. Davidson wrote:
>>
>>> But*DARPA*and*NIST
>>> have recently developed a cesium clock, with 1x10e11 accuracy,
>>> that is the size of a grain of rice and is expected to initially
>>> cost less than $200.
>>
>> Hmmm... That could be used in a wrist watch. Imagine, a stratum 1 clock on
>> your wrist!
>
>It's hard to read the time accurately off something the size of a grain of
>rice ;-)

It'll have to be put into an hearing aid. The trick is going to
be designing the right interface... Perhaps voice recognition?

You'll see people walking along, saying apparently to themselves
"What time is it?" (And of course only they will hear the
answer.)

--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@barrow.com

Floyd L. Davidson wrote:

> You'll see people walking along, saying apparently to themselves
> "What time is it?"**(And*of*course*only*they*will*hear*the
> answer.)

But they'd also have to put up with the continuous ticking of the
clock. ;-)

On Sat, 15 Jan 2005 00:27:54 -0900, Floyd L. Davidson wrote:

>>> Floyd L. Davidson wrote:
>>>
>>>> But*DARPA*and*NIST
>>>> have recently developed a cesium clock, with 1x10e11 accuracy,
>>>> that is the size of a grain of rice and is expected to initially
>>>> cost less than $200.
>>>
>>> Hmmm... That could be used in a wrist watch. Imagine, a stratum 1 clock on
>>> your wrist!
>>
>>It's hard to read the time accurately off something the size of a grain of
>>rice ;-)
>
> It'll have to be put into an hearing aid. The trick is going to
> be designing the right interface... Perhaps voice recognition?
>
> You'll see people walking along, saying apparently to themselves
> "What time is it?" (And of course only they will hear the
> answer.)

That would be fine, being a nutter walking along talking to yourself has
become socially acceptable since handsfree set for mobile phones became
available.

If the Linux system in which it is embedded works on VR then you will hear
people walking along talking to themselves saying stuff like "liss space
dash ell pipe grep myconfig dot conf".

--
Mark South: World Citizen, Net Denizen

Mark South wrote:

> It's hard to read the time accurately off something the size of a grain of
> rice ;-)

If it looks like a grain of rice, someone might come up with the slogan
"Takes a licking and keeps on ticking." ;-)