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Domain Time II > v5 > Configuration > Server > Configure Domain Time Server as a PTP Master

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Obtain The Time Configure Domain Time Server as a PTP Master
Domain Time II Server
Version 5.2

Please review the Planning and Recommended Configurations pages before proceeding.

In order to use Domain Time as a PTP Master, you must make the following configuration choices on the Obtain the Time property page on the Domain Time applet:

  1. Choose the Set this machine's clock by querying a list of servers radio-button.

  2. You may configure Domain Time Server as either the primary Grandmaster clock (using the Default, Enterprise, or Telecom profile), or as a backup master (using the Default or Enterprise profile).

    If this machine will be the primary Grandmaster on the network:

    1. Configure Domain Time Server to get its time from at least one (preferably three or more) trusted external time sources using either the DT2 or NTP time protocols. Note: You cannot configure Domain Time Server to obtain the time via PTP from a different master and also simultaneously serve the time using PTP (i.e. act as a boundary clock).

      By default, Domain Time Server will not act as a PTP Master unless it is correctly setting its own time from external sources. If you are on a closed network with no access to external time sources (or you have an internal clock card that sets the internal system clock time), you may set Domain Time Server to use the internal Windows clock as its source. To do this:

      1. Uncheck the Refuse to serve time until this machine's clock has been set checkbox.
      2. Uncheck or remove all listed time sources from the Time Sources list box. Note, Domain Time considers having no listed time sources to be an error condition, but it isn't in this case. To reduce extra logging, you can adjust the Check interval with get the time fails setting on the Timings property page.

      Note: On versions, prior to 5.2.b.20200930, per the IEEE 1588 2008 RFC's the Priority 1, Priority 2, and clock accuracy are automatically set to minimum values (regardless of how you have them configured), which may prevent the server from winning the Best Master Clock election. To workaround this limitation on older versions, uncheck all time sources in the list box, then Add a new NTP time source using localhost as the host name. That way, Domain Time Server will look at itself to get the time when it starts. The PTP Server will then use the local clock as its source, but serve time using PTP with the Priority 1, Priority 2, and Clock Accuracy settings as you've configured them.

      On version 5.2.b.202020930 and later, PTP configuration settings are always honored, so we recommend you upgrade if possible.

      See the Obtain the Time property page for more info on configuring time sources.

    2. Check the Analyze time samples and choose the best, or average equally good samples checkbox. This ensures Domain Time Server will select the most accurate time from among your listed sources.

    3. On the Timings property page, set both the Check Interval when able to get and correct the time and Check Interval when getting the fails settings to use the same fixed period, i.e. every 1 minute.

    4. On the Domain Role property page, uncheck both the Enable cascade signals and Enable Advisory signals checkboxes. If you have other Domain Time Servers, you may consider disabling these settings on those machines as well. These signals help Domain Time machines running NTP or DT2 protocols to converge more quickly across your domain, but the extra sync triggers can cause problems for Domain Time PTP slaves by shortening their sample collection period unexpectedly.

    5. If this machine will be a backup master using the Default or Enterprise profiles, also configure the machine to be a PTP slave as described above. Telecom profile masters cannot be configured as backup slaves.

  3. Be sure the Enable IEEE 1588 Precision Time Protocol (PTP) checkbox is checked, then click the Options link to display the IEEE Precision Time Protocol Options page. Review the listed options for PTP Domain, PTP Profile, Delay Transport, and IPv6 Scope to be sure they're set as you'd like. In most cases, the default settings are correct. An exception to this is if your Domain Time Server is already configured as a PTP Slave. Note: You cannot configure Domain Time Server to be a Master in the same domain as an existing Master. Use the PTP Domain: setting to select a different domain number.

    Domain numbers from 0-127 are assumed to be PTP v2.0 domains unless overridden on the Master Options dialog. Domains above that range are always assumed to be v2.1.

  4. Then, click the button to display the Master Options dialog page. Check the Allow this machine to become a PTP server checkbox. Domain Time will then participate in the PTP Best Master Clock election process.

  5. If the Send PTP v2.1 messages regardless of Domain number checkbox is checked, Domain Time will act as a v2.1 Master regardless of the domain number selected on the PTP Options page. Otherwise, it will serve v2.0 if the domain is between 0-127 and v2.1 if it is above that range.

  6. Decide if you want to be a Two-Step Master. As of v5.2.b.20190331, Domain Time can act as either a One-Step (Sync messages only) or Two-Step (Sync and Sync Followup messages) Master clock. In some environments, Two-Step operation can help slightly with accuracy, at a cost of doubling Sync traffic. In most cases, acting as a One-Step master is preferred.

  7. Select the delay transport you want Domain Time Server to use:

    Unicast Telecom subscriptions if you want Server to act as a Telecom master server.
    Multicast using IPv4 if you want Server to act as a Default or Enterprise profile server over IPv4. (default)
    Multicast using IPv6 if you want Server to act as a Default or Enterprise profile server over IPv6.

  8. Set multicast hop counts if using the Default or Enterprise profiles. If your PTP Master is not on the same subnet as its slaves, be sure the Multicast IPv4 TTL (Hop count for IPv6) settings on the Server's Broadcasts and Multicasts property page are set high enough to allow multicasts to cross intervening switches and routers. Typically you would set this value at least one higher than the number of router hops involved. Note your Slaves must also have their router hops values configured to allow their multicasts to cross any boundaries.

  9. If you want Domain Time to sign messages with PTP v2.1 authentication, you need to select the KeyId for each type of message you want to authenticate. You can only choose KeyIds for SHA256 hashes that have been enabled on the Symmetric Keys property page. Signing creates extra overhead that can affect accuracy, so choose to use only those messages that you require. In most cases, signing Announce messages provides a sufficient level of security at minimum impact. See the PTP v2.1 Authentication knowledgebase article for more information.

  10. Verify the Priority 1 and 2 values domain Time will when participating in the PTP Best Master Clock election process.

    1. If this machine is to be the Grandmaster, set the Priority 1 and 2 values so that it has higher precedence (a lower numeric value) than any other PTP device on the network.
    2. If this machine is not to be the Grandmaster, set the Priority 1 and 2 values so that it has lower precedence (a higher numeric value) than the Grandmaster priority settings.

  11. Set the TAI-UTC offset to reflect the current number of UTC leap seconds. The simplest way to get the correct current global count of UTC leap seconds is to issue this command from an elevated command prompt which imports the data from IETF servers:

      dtcheck -leapfile -y

    Otherwise, you can manually enter the TAI-UTC offset into the registry by entering the number of leapseconds into this registry key (create it if not present):

      Node: HKLM\SOFTWARE\Greyware\Domain Time Server\Time Sources\PTPv2 (IEEE 1588)
      Type: Reg_DWORD
      Key Name: TAI-UTC Offset Discovered (seconds)

  12. Restart the Domain Time Server service. You may check the activity of the PTP conversations by clicking the Status and Graph links.


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