[Nottingham] "ntpq -p" displayed flags

Chris Booth Chris.Booth at nottingham.ac.uk
Wed Jan 25 12:48:51 UTC 2012

Hi Martin,

Couple of links you could add:


http://www.ietf.org/rfc/rfc1305.txt  or the pdf at: http://www.rfc-editor.org/rfc/rfc1305.pdf

The meanings (that you have already gathered together on your web page) of  ntpd -p's output are explicitly explained in:  /usr/share/docs/ntp-4.2*/debug.html  from where I get this quote: "The mean millisecond time offset (phase) and deviation (jitter) monitor the clock quality".  So *I guess* that means that the jitter number printed is a value indicating a range to indicate the accuracy of the phase value. 

http://www.ietf.org/rfc/rfc1305.txt  has more details on how NTP is to handle the random noise (jitter) of hardware clocks, or fluctuations (jitter) in the network.  It also has an interesting explication of the changes in and relations between our timekeeping systems over the past 5,000 years or so - worth a quick read.

.PTB. are the German timekeepers.
.DCFa. is from an NTP radio receiver.


Chris Booth

-----Original Message-----
From: nottingham-bounces at mailman.lug.org.uk [mailto:nottingham-bounces at mailman.lug.org.uk] On Behalf Of Martin
Sent: 25 January 2012 01:39
To: Notts GNU/Linux Users Group
Subject: Re: [Nottingham] "ntpq -p" displayed flags


> Anyone know what the characters mean in the first column of the "ntpq 
> -p" output?
> I've got a collection of: "x# +*"
> And I ain't seen where they are described!...
> Anyone know rather than me making a quality guess? (Note the pun for 
> those that might know :-) )

I've webbed up what I've gleaned so far:

"ntpq -p" output

Corrections and further details welcomed. Can anyone comment to clear up the "?"s and answer whether the jitter value is the range or a +/- value?

Fill in the gaps?

Hope of interest,


Martin Lomas
martin at ml1.co.uk

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