[time-nuts] NTP stratum 0

Magnus Danielson cfmd at bredband.net
Sat Jan 14 15:00:23 EST 2006


From: "Rob Kimberley" <time.bandit at btinternet.com>
Subject: Re: [time-nuts] NTP stratum 0
Date: Sat, 14 Jan 2006 18:48:16 -0000
Message-ID: <!&!AAAAAAAAAAAYAAAAAAAAAOYAZyOzV8ERq+LmT45ypI7CgAAAEAAAAAzy/YBW0+RBmivoTTPkkh0BAAAAAA==@btinternet.com>

> The Stratum numbers in the Telecom Sync industry and those used in NTP
> hierarchy are different beasts.

I agree, they are completely different beasts.

> In Telecom Sync, Stratum 1, 2, 3 et al are internationally defined levels of
> frequency accuracy.

Um, no. They are nationally specified in the USA. You find them in ANSI T1.101.
For their international variants you have to go to ETSI EN 300 462 series, as
well as the ITU-T Rec. G.810 to G.813. Neither the ETSI or ITU-T standards uses
Stratum indications, instead they use designations such as PRC, SSU and SEC.

> In NTP Stratum 1 merely means the top of the hierarchical pyramid with
> Stratum 2, 3 etc below it.

Indeed. It is really just a reference chain length from whatever the reference
is, which may anything form a Ceasium-beam with coordinated time to an
undiciplined XO.

> Stratum 0 has been used in discussions I have seen from people at Datum
> and TrueTime to represent a GPS/NTP reference, but realistically I believe
> that it should be labelled as Stratum 1.

Indeed.

> Would  humbly suggest you take a look at www.ntp.org for more information.

Also, the references from earlier this thread adds up. The RFC 1305 is as such
a very interesting article.

Cheers,
Magnus




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