Interesting stratum 1 NTP clock

Robert E. Seastrom rs at
Tue Jul 7 14:42:45 UTC 1998

   From: Shawn David Solomon <sdsolomo at>

    I'm glad we've wandered upon the topic of stratum 1 clocks.  I've been
   looking for a clock that has the capability to provide clocking to Cisco
   ATM switches (BPX's) and also provide a clock source for our unix hosts.
   Do they make such a beast?  is it a good idea to use the clock for both

Actually, you're looking for two different things here:

1) a frequency standard that is traceable to a cesium or rubidium
frequency source, with an output of 1 MHz, 10 MHz, 100 MHz, or
whatever the PLL in the Cisco wants to see to discipline the line
clocking, and

2) a time standard (synchronized to USNO) with a 1PPS output that is
synchronized to the top of the second.

My question would be, what is the goal here?  All of the integrated
plug-n-play NTP servers represent a tradeoff of money for time, but
that may well represent a wise choice if you don't have someone on
your staff who has built a stratum 1 NTP server before.  If there is
some reason to use the same clock for both?  If not, there is a pretty
good chance that you can set up two separate units, a GPS-based unit
for the computers and a Cs or Rb standard for the ATM switch for less
money than you would pay for a brand new integrated unit.  This is
particularly true if you're handy with surplus shops -- I have seen Rb
standards going for as low as $800 (working, with plenty of life left
in the tube), and if you have plenty of time and access to an
already-calibrated frequency standard, even the calibration is well
within the capabilities of any reasonably advanced technical

If you want to talk more about this, let's take it offline before
someone sends me email telling me that NTP is not an operational issue
(bah!).  :)


PS:  links o' the day (bouquet of options from ready-made to roll-your-own):

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