On 10/14/2010 5:22 PM, Michael Bilow wrote:
On 2010-10-14 17:07, Bruce Labitt wrote:
On 10/13/2010 9:25 AM, Jerry Feldman wrote:
When: October 20, 2010 7PM (6:30PM for Q&A)
Topic: Hardware Hacking: Atomic Clock Building
Moderators: Federico Lucifredi, Product Manager, Novell
Location: MIT Building E51, Room 325
Federico builds an atomic clock out of a pocket-sized
Sheevaplug device
Any one go to this? What was used as the clock? How does
it get to be stratum-1? That is reserved for a decent
clock, IIRC? As in a primary reference, like caesium?
Anyone got a link on the primary ref clock? I checked out
the sheeva plug and its thermally mismanaged variants. The
concept is tres cool. The thermal issues, not so good. Any
list members have first hand experience with wall-wart
computers?
Technically, a Stratum-1 NTP clock means that it is
traceable to a NIST reference by means other than NTP. The
accuracy of the clock is stated in NTP messages. As a
result, a Stratum-N clock could be more accurate in
absolute terms than a Stratum-1 clock (although obviously
not the one to which it is itself traceable).
For example, it's quite common for a Stratum-2 NTP peer to
be within 25ms of absolute accuracy if it is referenced to
a very good Stratum-1 NTP peer. If someone set up a lousy
Stratum-1 NTP peer capable of only 100ms of absolute
accuracy, this would be perfectly legal although fairly
useless.
-- Mike
According to the announcement:
"Using the lowest amount of custom hardware and pouring Perl and Shell
Script over everything as the glue binding it all, we create a
minimalistic device delivering a perfectly tuned network time source:
your very own stratum-1 ntp server, turning a pocket-sized Sheevaplug
device into your personal atomic clock."
and http://en.wikipedia.org/wiki/NTP_server#Clock_strata
snipped for your convenience:
Stratum 0
These are devices such as atomic (caesium, rubidium)
clocks <http://en.wikipedia.org/wiki/Atomic_clock>, GPS
clocks <http://en.wikipedia.org/wiki/GPS_clock> or other
radio clocks <http://en.wikipedia.org/wiki/Radio_clock>.
Stratum-0 devices are traditionally not attached to the
network; instead they are locally connected to computers
(e.g., via an RS-232
<http://en.wikipedia.org/wiki/RS-232> connection using a
Pulse per second
<http://en.wikipedia.org/wiki/Pulse_per_second> signal).
Stratum 1
These are computers attached to Stratum 0 devices.
Normally they act as servers for timing requests from
Stratum 2 servers via NTP. These computers are also
referred to as time servers
<http://en.wikipedia.org/wiki/Time_server>.
I would think this implies the Sheevaplug is connected to a Stratum-0 source.
What was the
source that Federico used? Anyone know?
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