Hi,
I have a machine that is syncing to a Stratum-2 server which is
syncing to a Stratum-1 server, which has a GPS Stratum-0 device
attached to it. At my work (financial services) the market rules
mandate synchronizing our clocks to within a maximum 3 second
difference of the NIST atomic clock. We also need to log/document
that we are within 3 seconds.
So I have been perusing the output of ntpq but I don't fully
understand it after some time of study. I assume I could use the pe
command to figure out what my current offset is, and then as to
determine my assID, and finally rv <assID> to look at my peers. Then
I could perhaps add the current offset of my current peer, to one of
the numbers from the rv command (rootdispersion?), to arrive at a
maximum offset from my Stratum-1 server, and thus from NIST time (+-
100 microseconds or whatever the guarantee is for the Stratum-0
device). When I say "guarantee" I really think we're talking about
best effort. BTW, RFC1305 says that rootdispersion is in seconds but
I think it's really in milliseconds.
Can anyone help? Given the below results from ntpq, what numbers
would I need in order to determine my maximum deviation from NIST time
at this current point in time? Can I even determine that from my
client machine here, or do I need to login to all servers: Client,
plus Stratum-2, plus Stratum-1, to arrive at a legitimate value?
Thanks.
ntpq> pe
remote refid st t when poll reach delay
offset jitter
==============================================================================
*XX.XX.XX.21 XX.XX.XX..1 2 u 236 1024 377 0.390
-0.060 0.017
+XX.XX.XX..22 XX.XX.XX.1 2 u 980 1024 377 0.333
1.797 0.081
127.127.1.0 .LOCL. 10 l 39 64 377 0.000
0.000 0.001
ntpq> as
ind assID status conf reach auth condition last_event cnt
===========================================================
1 11015 9614 yes yes none sys.peer reachable 1
2 11016 9414 yes yes none candidat reachable 1
3 11017 9014 yes yes none reject reachable 1
ntpq> rv 11015
assID=11015 status=9614 reach, conf, sel_sys.peer, 1 event,
event_reach,
srcadr=XX.XX.XX.21, srcport=123, dstadr=YY.YY.YY.16, dstport=123,
leap=00, stratum=2, precision=-18, rootdelay=106.873,
rootdispersion=7.431, refid=10.30.25.1, reach=377, unreach=0, hmode=3,
pmode=4, hpoll=10, ppoll=10, flash=00 ok, keyid=0, ttl=0,
offset=-0.060,
delay=0.390, dispersion=18.684, jitter=0.017,
reftime=cce8d703.3ffd812a Tue, Dec 9 2008 5:37:39.249,
org=cce8fc6c.762843fb Tue, Dec 9 2008 8:17:16.461,
rec=cce8fc6c.763b45df Tue, Dec 9 2008 8:17:16.461,
xmt=cce8fc6c.761d72f9 Tue, Dec 9 2008 8:17:16.461,
filtdelay= 0.43 0.39 0.50 0.36 0.41 0.46 0.42
0.45,
filtoffset= -0.08 -0.06 -0.10 -0.23 -0.31 -0.41 -0.46
-0.58,
filtdisp= 0.00 15.38 30.77 46.13 61.50 76.85 92.21
107.60
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