[time-nuts] NTP stratum 0
M. Warner Losh
imp at bsdimp.com
Sat Jan 14 12:53:40 EST 2006
In message: <20060114164520.GA25156 at feynman>
Neal McBurnett <neal at mcburnett.org> writes:
: On Sat, Jan 14, 2006 at 05:25:04PM +0100, TwoSpades wrote:
: > I would like to know where could I find the FORMAL specification of the NTP
: > stratum 0.
: > I often read that it can be a GPS receiver, but I think that there must be a
: > formal definition
: > of the characteristics of that device.
Well, it depends on what you mean by formal. The 'rough and ready'
definition for stratum 1 time servers is that they are synchronized to
a time source better than they would get from another ntp server. If
your system time can be synchronized to within a few tens of
microseconds with the receiver you have, then you are definitely
stratum 1 material. If you relax the requirement to be only as good
as you need to be to serve time over the internet, then I'd say that
requirement drops to about 1ms.
In general, you want the server to be traceable back to the official
time, as produced by some time authority. For a simple ntp server,
that tracking doesn't have to be too precise, from a time geeks point
of view. If you are within about a millisecond, then no one will
notice if the time exchange is over the internet...
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