Joachim Schrod wrote:
Brian Utterback wrote:
So, I still think that at least three servers would be a good idea.
I am thinking that if you pick three servers, and configure each
of them with three independent Internet servers and have them peer
with each other, that you will have a pretty robust system with
a minimum of administrative overhead. This assumes that the choice
of pool servers will be independent between them.
That's interesting. Lurking on this group I had always the impression
that using stratum 1 servers for small companies is frowned upon. But
now both your answer and the answer by Richard point into a different
directions, namely to use them as well: If I have three different
independent Internet servers for three internal servers, I need nine
Internet servers. (In the case of four x four servers, I need 16
Internet servers.)
Not quite so! If you are serving time to 100 clients, you can justify
using a stratum 1 server. There are, however, too many people using
stratum 1 servers with no justification whatever except that they can!
Nobody can stop you from using the NIST servers but you can probably do
better elsewhere unless you happen to be right next door to one.
Pick some nearby servers from the stratum two list and try them out.
Keep testing stratum two servers until you find some that work well for
you. You should look for low values of delay and jitter or dispersion.
If you want a stratum one server you can be one for a mere $200 US and
some effort on your part. I operate two stratum one servers in my home;
one synchronizes to a GPS receiver and the other to a WWV receiver. The
GPS works much better but both are technically stratum 1. All you need
is a GPS receiver and the ability to locate an antenna where it will
have an unobstructed view of the sky. My GPS synchronized server
maintains an accuracy of about +/- 2 microseconds. YMMV.
The pool delivers only three servers per region (with multiple IP
numbers, but that is for load balancing, as far as I understand). That
means that one either has to use another national pool which is often
not as near net-wise. Or one selects 6 or 13 other Internet servers.
When I look at the public stratum 2 servers at
http://ntp.isc.org/bin/view/Servers/StratumTwoTimeServers, I'm hard
pressed to find 6 or 13 servers in Germany or nearby Europe. That means
I have to resort to stratum 1 servers.
If you want to use four peered servers you need a minimum of seven
upstream servers to do it right; one unique server for each of your
servers and three others to be shared by all. Do you REALLY need four
peered servers? How about two servers, one with a GPS refclock and one
with a DCF77 refclock? Peer the two with each other.
Is this really the recommendation that I should formulate for the NTP
Support Wiki? That's why I asked how many company servers should sync to
Internet servers.
When you get a configuration that works for you, then you can consider
writing an article for the Wiki. If you have done something really
unique and clever you should definitely write about it.
<snip>
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