[ntp:questions] Need to verify the offset

Todd Snyder tsnyder at rim.com
Tue Dec 9 21:37:56 UTC 2008


I am currently looking to do something similar.  My requirements are
longer term, and much more accurate (we're aiming for 5ms across a large
number of servers).

I did some poking around, and I found this perl script and have been
fiddling with it.  I wish I was more of a time nerd (no offense meant)
and could understand all the output, but I think what you (and I) want
is here somewhere:

 http://www.kloth.net/software/sntp.php

In particular, it calculates how far off the polled server is from the
source you're querying from.  If you were/I were to query from my master
ntp clock to all servers, on a frequent basis, we'd be able to see
changes and report on them fairly easily.

I am trying to find something a little more robust and enterprise
quality, but this will do until I can do that.  Someone out there must
have written something enterprise class to monitor time across a
network, I just need to find them!

Cheers,

Todd. 

-----Original Message-----
From: questions-bounces+tsnyder=rim.com at lists.ntp.org
[mailto:questions-bounces+tsnyder=rim.com at lists.ntp.org] On Behalf Of
Hushpuppy
Sent: Tuesday, December 09, 2008 11:30 AM
To: questions at lists.ntp.org
Subject: [ntp:questions] Need to verify the offset

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

_______________________________________________
questions mailing list
questions at lists.ntp.org
https://lists.ntp.org/mailman/listinfo/questions

---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful.



More information about the questions mailing list