[ntp:questions] which servers should be peers?

Charles Elliott elliott.ch at verizon.net
Wed Sep 18 10:32:50 UTC 2013


IMHO, you don't want 15 servers; you want 9.  You could start out with 15
and ntpd will mark the ones it finds lacking with a #.  After a few days
you could then whittle the list down to 9 based on the ones most
frequently marked with a #.  I am fairly sure ntpd only uses 9 servers
in its final filtering and smoothing algorithms.

I suggest you pick servers that are close to you.  Accuracy is heavily
influenced by distance, as it the possibility of congestion increasing
jitter.

I would and do use stratum 2 servers.  At least in the U.S., the
stratum 1 servers are so heavily overloaded that at the end of the
day you will have more accurate time with stratum 2.

This is highly controversial, and many on this list will say its
abusive, but I use the iburst keyword and minpoll 4 (16 secs) maxpoll 5 
(32 secs).  Otherwise, when the Internet becomes busy and a wave of
congestion flows thru the system, the higher poll rates greatly slow
ntpd's recovery of accurate time.  For the same reason, I use the
keyword line:

tinker huffpuff 7200

I believe it produces a moderate improvement.

Charles Elliott

> -----Original Message-----
> From: questions-bounces+elliott.ch=verizon.net at lists.ntp.org
> [mailto:questions-bounces+elliott.ch=verizon.net at lists.ntp.org] On
> Behalf Of Maria Iano
> Sent: Monday, September 16, 2013 11:25 AM
> To: questions at lists.ntp.org
> Subject: [ntp:questions] which servers should be peers?
> 
> I have four data centers all able to communicate both over our internal
> network and over the internet. I have a stratum 1 ntp appliance
> pointing to GPS at each data center; so a total of 4. Each appliance
> has an interface on our internal network and an interface on the
> external internet-routable network. I am getting ready to deploy 12
> physical servers which will act as stratum 2 ntp servers. I'm not
> primarily doing this to spread the load, but to try to cope with a
> worst case scenario in which all of our stratum 1 servers suddenly go
> insane.
> 
> Each data center will have at least one of these stratum 2 servers on
> the internal network and one on the external network. Our internal
> clients will point to the stratum 1 appliances and the internal stratum
> 2 servers, and our external clients will point to the stratum 1
> appliances and external stratum 2 servers.
> 
> From my reading, I believe that each stratum 1 appliance should peer
> with all 15 other servers, both stratum 1 and stratum 2. Is that
> correct? Assuming that is correct, my question is whether I should have
> all of the stratum 2 servers peer with all 15 others as well?
> 
> I appreciate any advice you can give.
> 
> Thanks,
> Maria
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