NTP statistics

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This page is related to the Control Center interface present on the HMP devices.

Description

Date/Time > NTP Statistics

The following NTP information is displayed within HMP Control Center:

  • Server IP.
  • Stratum
    A static measure representing the number of servers up to a reference time server (usually an atomic clock).
  • Status:
    • peer - this is the server used for the time synchronization;
    • candidate - this is a server whose time is consistent with the HMP and may be used in case the peer is no longer available;
    • reject - the server is not used, because its stratum is too low or it has been configured as "Monitor only" in the Time Sources;
    • oulier - the server is too different from the peer to be used for synchronization;
    • initializing - during transition phase or when it cannot be reached;
    • unreachable - the server cannot be reached.
  • Reach
    How often the server has been reached as a percentage within the last 8 attempts; it should be as close as possible to 100%.
  • Time offset
    The time difference in milliseconds between the HMP time and the NTP server time.
  • Delay
    The time delay in milliseconds between the moment the HMP has send the request and got the answer from the NTP server; it should be as small as possible.
  • Dispersion
    When repeatedly reading the time, the time offset may vary almost randomly and the difference (second derivation) of these time offsets is called jitter or dispersion. Note that a small value is needed for synchronized content.
  • Poll interval
    The time interval between requests towards the NTP server. It will start with the minimum value and gradually increase up to the maximum value; for internal NTP servers (min, max) = (16s, 256s) and for public ones (min, max) = (64s, 1024s).

After the NTP statistics, the information regarding the local clock calibration is displayed. The correction is displayed in ppm (part per million); for instance 1ppm would mean that the internal clock will drift with 32 seconds in a year.

Troubleshooting

  • In case some of your NTP server can't be reached ("Status" column remains always "Initializing"), it may be behind a firewall or just wrongly configured. Check the NTP server configuration with your system administrator.
  • The values in the column "Time offset" should be as close to 0 as possible, it this is not the case, then it might be necessary to either check the network configuration or change the NTP server.
  • The NTP server might be rejected if the dispersion value is hight, at least higher than the time offset.
This page was last modified on 29 April 2016, at 16:12.