[ntp:questions] how to have offset < 1ms
Richard B. Gilbert
rgilbert88 at comcast.net
Mon Apr 12 20:35:46 UTC 2010
lhommedumatch wrote:
> I have my PC clock synchronised with a ntp server (ntpgmtaceb).
>
> With ntpq -p, I see an offset of 6ms.
> How can I be sure to have an offset < 1ms
>
> ntpq -p
> remote refid st t when poll reach delay
> offset jitter
> ==============================================================================
> LOCAL(0) .LOCL. 10 l 61 64 377 0.000
> 0.000 0.001
> *ntpgmtaceb .1PPS. 1 u 709 1024 377 29.431
> -6.450 0.917
>
> Here is my ntp.conf:
> # Permit time synchronization with our time source, but do not
> # permit the source to query or modify the service on this system.
> restrict default kod nomodify notrap nopeer noquery
>
> # Permit all access over the loopback interface. This could
> # be tightened as well, but to do so would effect some of
> # the administrative functions.
> restrict 127.0.0.1
> restrict -6 ::1
>
> # Hosts on local network are less restricted.
> #restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
>
> # Use public servers from the pool.ntp.org project.
> # Please consider joining the pool (http://www.pool.ntp.org/
> join.html).
>
> #broadcast 192.168.1.255 key 42 # broadcast server
> #broadcastclient # broadcast client
> #broadcast 224.0.1.1 key 42 # multicast server
> #multicastclient 224.0.1.1 # multicast client
> #manycastserver 239.255.254.254 # manycast server
> #manycastclient 239.255.254.254 key 42 # manycast client
>
> # Undisciplined Local Clock. This is a fake driver intended for backup
> # and when no outside source of synchronized time is available.
> server 127.127.1.0
> fudge 127.127.1.0 stratum 10
>
> # Drift file. Put this in a directory which the daemon can write to.
> # No symbolic links allowed, either, since the daemon updates the file
> # by creating a temporary in the same directory and then rename()'ing
> # it to the file.
> driftfile /var/lib/ntp/drift
>
> # Key file containing the keys and key identifiers used when operating
> # with symmetric key cryptography.
> keys /etc/ntp/keys
>
> # Specify the key identifiers which are trusted.
> #trustedkey 4 8 42
>
> # Specify the key identifier to use with the ntpdc utility.
> #requestkey 8
>
> # Specify the key identifier to use with the ntpq utility.
> #controlkey 8
> server ntpgmtaceb
> restrict ntpgmtaceb mask 255.255.255.255 nomodify notrap noquery
>
> Regards,
> Ludovic
Read the documentation CAREFULLY! I think that you will find that
"offset" is NOT the difference between your clock and the correct time!
There IS a number that does represent the difference between your clock
and the correct time but I have forgotten what it's called.
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