[ntp:questions] noise and stability values

Jaap Winius jwinius at umrk.nl
Sat Aug 28 21:22:38 UTC 2010


On Sat, 28 Aug 2010 19:57:41 +0000, Danny Mayer wrote:

> Can you post a before and after snapshot of what you are talking about
> so that we can get an idea of what you are seeing/not seeing?

Sure thing. Here's the output from before with Debian lenny:

~$ ntpq -c rv
assID=0 status=06f4 leap_none, sync_ntp, 15 events, event_peer/strat_chg,
version="ntpd 4.2.4p4 at 1.1520-o Sun Nov 22 17:34:54 UTC 2009 (1)",
processor="i686", system="Linux/2.6.26-2-686", leap=00, stratum=2,
precision=-20, rootdelay=15.422, rootdispersion=42.607, peer=16773,
refid=153.60.75.10,
reftime=d023ea90.fe15c294  Sat, Aug 28 2010 22:05:36.992, poll=10,
clock=d023f19e.a891bc36  Sat, Aug 28 2010 22:35:42.658, state=4,
offset=0.188, frequency=-8.335, jitter=0.322, noise=0.216,
stability=0.018, tai=0
~$ _

The stuff I've been graphing is near the end: offset, frequency, jitter, 
noise and stability. The noise variable, however, is not mentioned on the 
old documentation page for ntpq (dated 04-Nov-2009 0:12 UTC).

And here's what it looks like now with Debian squeeze:

~$ ntpq -c rv
associd=0 status=0415 leap_none, sync_uhf_radio, 1 event, clock_sync,
version="ntpd 4.2.6p2 at 1.2194-o Tue Jul 13 19:08:49 UTC 2010 (1)",
processor="i686", system="Linux/2.6.32-5-686-bigmem", leap=00, stratum=1,
precision=-19, rootdelay=0.000, rootdisp=0.295, refid=PPS,
reftime=d023f1a8.dcbc53c3  Sat, Aug 28 2010 22:35:52.862,
clock=d023f1ac.f06ad780  Sat, Aug 28 2010 22:35:56.939, peer=52502, tc=4,
mintc=3, offset=0.000, frequency=-2.698, sys_jitter=0.002,
clk_jitter=0.002, clk_wander=0.000, host="bitis", flags=0x80001,
digest="md5", signature="md5WithRSAEncryption", update=201008250323,
cert="bitis bitis 0x0", until=200912202320
~$ _

Offset and frequency are still present while there are now two types of 
jitter, but the noise and stability variables have apparently 
disappeared. Mention of the stability variable has also been omitted from 
the new ntpq documentation page (dated 04-Nov-2009 0:12 UTC).

Cheers,

Jaap




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