[ntp:questions] Re: Mother Of All Clocks

Todd Knarr tknarr at silverglass.org
Sun Mar 27 18:37:19 UTC 2005


In comp.protocols.time.ntp <88e50c98.0503261447.2849adc7 at posting.google.com> Heiko Gerstung <hg at heiko-gerstung.de> wrote:
> several millions of transactions per day. It is simply necessary for
> them to ensure that all their networks (which are physically separated
> due to security reasons) including all database servers, workstations
> and routers are running with the same time coming from the same clock.

That wouldn't completely explain the need for that many stratum-1
servers, though. The only way I can see a need for 30+ stratum-1 sources
is if the timestamp requirements were so stringent that you _had_ to
have all clients sync'd directly to a stratum-1 to meet them and you had
so many clients that you needed that many servers to avoid overload. I'd
also want the stratum-1s physically seperated so loss of power or damage
to a rack didn't take down all my time sources at once.

Normally I'd have expected a dozen or so stratum-1s scattered around the
country syncing with each other (over their own dedicated network in
this case), and a number (depending on the number of clients) of
stratum-2 servers for each network that needs time service multi-homed
between the stratum-1 network and the network they serve and syncing to
non-overlapping subsets of the stratum-1s and sibling stratum-2s. I'd
expect that to give you better resistance to failure (short of failure
of the GPS system itself) and be cheaper as well. The only issue would
be time stability, which I'd expect to be on the order of no more than a
millisecond variation between the stratum-2s in this setup.

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