NTP (Network Time Protocol) (just:store v4.0)

Owned by Tobias Gotthard (Unlicensed)
Last updated: Oct 12, 2020 by Thomas Staiger
12 min read

Table of Contents

Preface

NTP (network time protocol) is a networking protocol for clock synchronization. It allows all just:store clients to have the same time, which can be useful when working on Adobe Premiere or DaVinci Resolve projects in groups.

Accessing the NTP Settings

Click on NTP in the sidebar. The NTP overview will be shown, allowing you to monitor and configure the NTP settings.

NTP Tracking Information

  • Reference ID: ID of the server to which just:store is currently synchronised.

  • Address: IP address of the server which is used for the synchronization.

  • Stratum: displays how many hops just:store is away from a computer with an attached reference clock.

  • Reference Time UTC: time at which the last measurement from the reference source was processed.

  • Local Time Offset: estimated local offset on the last clock update.

  • Frequency: is the rate by which the system’s clock would be wrong if chronyd was not correcting it.

  • Update Interval: is the interval between the last two clock updates.

  • Leap Status: can be Normal, Insert second, Delete second or Not synchronised.

NTP Source Information

  • State: indicates the source to which just:store is currently synchronised and also indicates other acceptable sources.

  • Mode: indicates the mode of the source. This can be a server, a peer or a reference clock.

  • Address: hostname or IP address of the source, or reference ID for reference clocks.

  • Stratum: shows the stratum of the source, as reported in its most recently received sample. Stratum 1 indicates a computer with a locally attached reference clock. A computer that is synchronised to a stratum 1 computer is at stratum 2. A computer that is synchronised to a stratum 2 computer is at stratum 3, and so on.

  • Polling: shows the rate at which the source is being polled, as a base-2 logarithm of the interval in seconds. For example, a value of 6 would indicate that a measurement is being made every 64 seconds.

  • Reach: shows the source’s reachability register printed as an octal number and is updated on every received or missed packet from the source. A value of 377 indicates that a valid reply was received for all from the last eight transmissions.

  • Last Receive: shows how long ago the last good sample was received from the source.

General NTP Settings

  • Server Address: indicates on which address the NTP server of just:store should send packages.

  • Server Port: sets the port on which the NTP server sends.

  • Client Address: indicates on which address the NTP server of just:store should be listened to. 

  • Client Port: sets the port on which the NTP server listens.

  • Used Sources: limits which sources are included in the combining algorithm. Their synchronisation distance has to be shorter than the distance of the selected source multiplied by the value of the limit.

  • Minimum Sources: sets the minimum of valid signals for getting the correct time.

  • Maximum Distance: sets the maximum allowed root distance of the sources to not be rejected by the source selection algorithm.

  • Stratum: sets the stratum of the server which will be reported to clients when the local reference is active. The specified value is in the range 1 through 15, and the default value is 10.

  • Distance: sets the threshold for the root distance which will activate the local reference.

  • Orphan Mode: when enabled, sources with stratum equal to the local stratum are assumed to not serve real-time. They are ignored unless no other source is selectable and their reference IDs are smaller than the local reference ID.

  • RTC Connection UTC: is for the RTC to keep Universal Coordinated Time (UTC). This does not suffer from the 1-hour problem when daylight saving starts or ends.

  • RTC Sync: periodically copies the system time to the RTC and the NTP service does not try to track its drift.

  • Allow All Requests: defines if the request should be filtered or if all should be accepted. If you set this option all request will be declined whether you set Deny All Requests.

  • Deny All Requests: indicates if the request should be general declined and checked to be accepted.

Reference Clocks

  • State: shows if the reference clock is activated or disabled.

  • Type: can be PPS, SHM, SOCK or PHC.

  • Clock: shows the available options of the reference clock.

  • Rate: sets the rate of the pulses in the PPS signal (in Hz).

  • PPS: forces the NTP server to treat any reference clock (e.g. SHM or PHC) as a PPS reference clock.

  • TAI: indicates if the reference clock keeps time in TAI instead of UTC and that the NTP server should correct its offset by the current TAI-UTC offset.

  • Required: at least one of the sources specified with this option is selectable before updating the clock. Together with the Always Trust option, this can be useful to allow a trusted, but not very precise, reference clock to be safely combined with unauthenticated NTP sources in order to improve the accuracy of the clock.

  • Preferred: prefer this source over sources without the preferred option.

  • Always Trust: assume time from this source is always true. It can be rejected as a falseticker in the source selection only if another source with this option does not agree with it.

  • Actions: allows you to edit or delete a reference clock.

Adding a Reference Clock

  1. Press the Add Reference Clock button.

  2. Configure the reference clock to your needs. The available options are documented below.

  3. Press the Add Ref. Clock button when you’re done.

Available Options

  • Type: can be PPS, SHM, SOCK or PHC.

  • Parameter: sets the parameters for the reference clock

  • Polling for external events: some drivers do not listen for external events and try to produce samples in their own polling interval. This is defined as a power of 2 and can be negative to specify a sub-second interval.

  • Polling: refresh interval for this source

  • Pulse per second: send a keep-alive message to avoid closing this connection.

  • State of the Source: shows if the reference clock is activated or disabled

  • Prefer this source: prefer this source over sources without the preferred option.

  • Require this source: this source must send a valid signal if this option is set because the time server gets the time as a primary signal from this source

  • Trust this source: assume time from this source is always true.
    It can be rejected as a false ticker in the source selection only if another source with this option does not agree with it.

  • Use TAI: sets that the reference clock keeps time in TAI instead of UTC and then network time protocol server should correct its offset by the current TAI-UTC offset

  • Rate: sets the rate of the pulses in the PPS signal (in Hz).

  • Stratum: this option sets the NTP stratum of the reference clock. This can be useful when the reference clock provides time with a stratum other than 0.

  • Noise Reduction: sets the length of the median filter which is used to reduce the noise in the measurements.

  • Offset correction: can be used to compensate for a constant error. The specified offset (in seconds) is applied to all samples produced by the reference clock

  • Maximum Lockage: specifies in a number of pulses how old can be samples from the reference clock specified by the lock option to be paired with the pulses. Increasing this value is useful when the samples are produced at a lower rate than the pulses.

Editing a Reference Clock

  1. Press the Edit button of the desired reference clock.

  2. Configure the reference clock to your needs. The available options are documented above.

  3. Press the Save NTP Reference Clock Settings button when you’re done.

Deleting a Reference Clock

  1. Press the Delete button of the reference clock you want to delete.

  2. Accept the dialog to delete the reference clock. The deletion cannot be undone.

NTP Syncing Server for NTP Server

  • Status: shows if the NTP server is activated or disabled.

  • Server Address: shows the IP address or hostname with the specific port.

  • Required: require that at least one of the sources specified with this option is selectable before updating the clock. Together with the Always Trust option, this might be useful to allow a trusted authenticated source to be safely combined with unauthenticated sources in order to improve the accuracy of the clock

  • Preferred: prefer this source over sources without the preferred option.

  • Always Trust: assume time from this source is always true. It can be rejected as a falseticker in the source selection only if another source with this option does not agree with it.

  • Polling

    • Min: specifies the minimum interval between requests sent to the server as a power of 2 in seconds.

    • Max: specifies the maximum interval between requests sent to the server as a power of 2 in seconds.

  • Requests: the target number of measurements to use for the regression algorithm which the NTP service will try to maintain by adjusting the polling interval between minimum polling and maximum polling.

  • Actions: allows you to edit or delete an NTP syncing server.

Adding an NTP Server

  1. Press the Add Server button.

  2. Configure the NTP server to your needs. The available options are documented below.

  3. Press the Add Server button when you’re done.

Available options

  • Hostname: the hostname or IP address of the server.

  • Port: port of the server.

  • State of Source: enable or disable this source.

  • Prefer this Source: prioritises the use of this source.

  • Require this Source: sets the source to be required or optional.

  • Trust this Source: define if and how to trust this source.

  • Maximum delay: sets the maximum delay between the request and the response.

  • Minimum/Maximum Polling: specifies the minimum/maximum interval between requests sent to the server.

  • Offset correction: specifies a correction (in seconds) which will be applied to offsets measured with this source.

  • Court of measurements: target number of measurements to use for the regression algorithm which the NTP service will try to maintain by adjusting the polling interval between minimum polling and maximum polling.

  • Improve accuracy of response: when enabled, the NTP service will shorten the interval between up to four requests to 2 seconds or less when it cannot get a good measurement from the server. 

  • Improve accuracy of requests: when enabled, the interval between the first four requests sent to the server will be 2 seconds or less instead of the interval specified by the minimum polling option, which allows the network time protocol service to make the first update of the clock shortly after the start.

Editing a NTP Syncing Server

  1. Press the Edit button of the NTP syncing server you want to edit.

  2. Configure the NTP syncing server to your needs. The available options are documented above.

  3. Press the Save NTP Server Settings button when you’re done.

Deleting an NTP Syncing Server

  1. Press the Delete button of the NTP syncing server you want to delete.

  2. Accept the dialog to delete the NTP syncing server. The deletion cannot be undone.

Peers of NTP Server

  • Status: shows if the NTP server is enabled or disabled.

  • Hostname: shows the IP address or hostname with the specific port.

  • Required: require that at least one of the sources specified with this option is selectable before updating the clock. Together with the always trust option, this might be useful to allow a trusted authenticated source to be safely combined with unauthenticated sources in order to improve the accuracy of the clock.

  • Preferred: prefer this source over sources without the preferred option.

  • Always Trust: assume time from this source is always true. It can be rejected as a falseticker in the source selection only if another source with this option does not agree with it.

  • Polling: 

    • Min: specifies the minimum interval between requests sent to the server as a power of 2 in seconds.

    • Max: specifies the maximum interval between requests sent to the server as a power of 2 in seconds.

  • Requests: the target number of measurements to use for the regression algorithm which the network time protocol service will try to maintain by adjusting the polling interval between minimum polling and maximum polling.

  • Actions: allows you to edit or delete peers.

Adding an NTP Peer

  1. Press the Add Peer button.

  2. Configure the NTP peer to your needs. The available options are documented above.

  3. Press the Add Peer button when you’re done.

Editing an NTP Peer

  1. Press the Edit button of the NTP peer you want to edit.

  2. Configure the NTP peer to your needs. The available options are documented below.

  3. Press the Save NTP Peer Settings button when you’re done.

Available Options

  • Hostname: the hostname or IP address of the NTP peer.

  • Port: the port of the NTP peer.

  • State of Source: enable or disable the new source.

  • Prefer this Source: prefer this source over other sources without this option.

  • Require this Source: defines if this source is required or optional.

  • Trust this Source: always trust this source.

  • Maximum delay: maximum delay between request and response.

  • Minimum/Maximum Polling: specifies the minimum/maximum interval between requests sent to the server.

  • Offset correction: specifies a correction (in seconds) which will be applied to offsets measured with this source.

  • Court of measurements: target number of measurements to use for the regression algorithm which the network time protocol service will try to maintain by adjusting the polling interval between minimum polling and maximum polling.

  • Improve accuracy of response: with this option, the NTP service will shorten the interval between up to four requests to 2 seconds or less when it cannot get a good measurement from the server. 

  • Improve accuracy of requests: with this option, the interval between the first four requests sent to the server will be 2 seconds or less instead of the interval specified by the minimum polling option, which allows the network time protocol service to make the first update of the clock shortly after the start.

Deleting an NTP Peer

  1. Press the Delete button of the NTP peer you want to delete.

  2. Accept the dialog to delete the NTP peer. The deletion cannot be undone.

Pools of NTP Server

  • Status: shows if the pool is enabled or disabled.

  • Hostname: shows the IP address or hostname with the specific port.

  • Required: require that at least one of the sources specified with this option is selectable before updating the clock. Together with the always trust option, this might be useful to allow a trusted authenticated source to be safely combined with unauthenticated sources in order to improve the accuracy of the clock.

  • Preferred: prefer this source over sources without the preferred option.

  • Always Trust: assume time from this source is always true. It can be rejected as a falseticker in the source selection only if another source with this option does not agree with it.

  • Polling: 

    • Min: specifies the minimum interval between requests sent to the server as a power of 2 in seconds.

    • Max: specifies the maximum interval between requests sent to the server as a power of 2 in seconds.

  • Requests: target number of measurements to use for the regression algorithm which the network time protocol service will try to maintain by adjusting the polling interval between minimum polling and maximum polling.

  • Actions: allows you to edit or delete pools.

Adding an NTP Pool

  1. Press the Add Peer button.

  2. Configure the pool to your needs. The available options are documented above.

  3. Press the Add Pool button when you’re done.

Editing an NTP Pool

  1. Press the Edit button of the pool you want to edit.

  2. Configure the pool to your needs. The available options are documented below.

  3. Press the Save NTP Pool Settings button when you’re done.

Deleting an NTP Pool

  1. Press the Delete button of the NTP pool you want to delete.

  2. Accept the dialog to delete the NTP peer. The deletion cannot be undone.

 

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