[ntp:questions] FreeBSD refclock error

Kevin Oberman oberman at es.net
Tue Aug 14 22:15:07 UTC 2007


> Date: Tue, 14 Aug 2007 14:05:40 -0700
> From: David Newman <dnewman at networktest.com>
> Sender: questions-bounces+oberman=es.net at lists.ntp.org
> 
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> On 8/14/07 5:51 AM, Jason Rabel wrote:
> >> ACK, thanks also for these tips.
> >>
> >> Next newbie question: Is ".GPS." the correct refid I should see?
> >>
> >> lancelot# ntpq -p
> >> remote      refid      st t when poll reach   delay   offset jitter
> >> =====================================================================
> >> *time.domain.tld .GPS.  1 u   33   64  377    0.746  -40.803 20.547
> >>
> > 
> > The 'refid', in this case 'GPS' is the source which time.domain.tld is
> > synced to. If it was synced to another NTP server then it would list its IP
> > there. You really should use more than one server to sync to... 4 is
> > generally the recommended minimum.
> > 
> 
> Thanks. Yet more newbie questions:
> 
> 1. Is it better to (a) list 4 sources on the box with the GPS receiver
> attached and just one source on all client boxes that point to it for
> ntp, or (b) list 4 servers on all boxes?

b) It's always best to have 3 (or more) servers for any box running ntp
as it allows the detection of broken servers and helps retain stability
in the event the stratum 1 server has a problem. 1 is a bad number as it
is a single point of failure. 2 is a bad number as it provides no clear
way of detecting who is wrong if the time starts drifting on one of the
servers. 
 
> 2. If (b) should I use the "prefer" directive to query the GPS-based
> server first?

No reason as it is stratum 1 and lower stratum clocks (and 1 is the
lowest) are always preferred over stratum 2 or higher.

If you have both your GPS and an external stratum 1 server, you might
want to prefer the internal one, but it would most likely be preferred
anyway as it would likely have lower delay (latency) and jitter.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 224 bytes
Desc: not available
URL: <http://lists.ntp.org/pipermail/questions/attachments/20070814/7a4e94e9/attachment.pgp>


More information about the questions mailing list