An example Linux host Ntp Platform Service Editor is shown in Figure 128. This is the default view for the RFC-1305 compliant NtpPlatformService on a Linux Supervisor host.
This dialog provides access to some key settings of the Network Time Protocol (NTP) Daemon on the Supervisor’s Linux OS.
Settings are only a small subset of those available—for all settings, plus the ability to make changes in the NTP Daemon,
use root login access of the Linux OS on the host. Refer to the Linux documentation about the NTP Daemon for specific details.
As in all Ntp Platform Service Editors, there are two main areas: Settings at top, Time Servers at bottom.
Settings in the Ntp Platform Service Editor Linux include the following properties:
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Enabled
If true, the host will use NTP to sync its clock with time values retrieved from other servers.
-
Sync Local Clock to NTP
If true, this enables the host to adjust its local clock by means of NTP. If disabled (false), the local clock free-runs at its intrinsic time and frequency offset. This flag is useful in case the local clock is controlled by some other device or protocol and NTP is used only to provide synchronization (as server) to other clients. In this case, the local clock driver can be used to provide this function and also certain time variables for error estimates and leap-indicators.
-
Use Local Clock as Backup
If true, should the specified NTP server(s) become unavailable at the time of a poll, the time used is provided by the system clock. This prevents the timing of the polling algorithm in the ntpd (which is executed at specified/changing intervals) from being reset.
-
Generate NTP Statistics
If true, the NtpPlatformService reports whatever information it can about its operation. To access these statistics with the station opened in Workbench, right-click the NtpPlatformServiceLinux and select ->. Keep in mind that the ntpd is a Linux process; thus NiagaraAX has no control over what it reports.
-
Authenticated Peers Only
If true (default), enables the server to synchronize with unconfigured peers only if the peer has been correctly authenticated using a trusted key and key identifier.
-
Autokey Regen Interval
Specifies the interval between regenerations of the session key list used with the autokey feature. Note that the size of the key list for each association depends on the interval and the current poll interval. The default value is 12 (units in NTP are in “log-base-two seconds,” or 2 to the power of
nseconds where 12 means 4096 seconds, or about 1.1 hours). For poll intervals about the specified interval, a session key list with a single entry will be regenerated for every message sent. -
Autokey Revoke Interval
Specifies the interval between regenerations of the private value used with the autokey feature.
-
Monitor
If true (default), enables the ntpd monitoring facility.
Each entry in the time servers list in the Ntp Platform Service Editor Linux specifies a server to which the host’s clock will be sync’ed when the service is Enabled (true), and “Use NTP on Server” is also true. These servers are not used if either of these properties are false.
Controls below the list allow you to add 
and delete 
servers, as well as reorder up 
or down 
. Fields for each time server includes the following:
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Address
Fully qualified domain name, IP address, or host files alias for the NTP time server.
-
Peer Mode
Peer mode to use with the server, as either server or peer (symmetricActive).
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Auto Key
If true, all packets sent to the address include authentication field encrypted using autokey scheme. If false, packets sent to the address include the authentication field encrypted using the specified Key identifier.
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Key
Applies only if Auto Key is disabled (false). To specify a key identifier, as an unsigned 32-bit integer less than 65536, used in authentication with packets set to the address.
-
Burst
False by default. If true, when server is reachable, upon each poll a burst of eight packets are sent, instead of the usual one packet. Spacing between the first and second packets is about 16 seconds to allow a modem call to complete, while spacing between remaining packets is about 2 seconds.
-
Preferred
If true, designates a server as preferred over others for synchronization. Note also that priority order (top highest, bottom lowest) is also evaluated if multiple servers are entered.
-
Min. Poll
Minimum poll interval for NTP messages, from 4 to 6. Note units are in “log-base-two seconds,” or 2 to the power of
nseconds (NTP convention), meaning from 2 to the 4th (16 seconds) to 2 to the 6th (64 seconds). -
Max. Poll
Maximum poll interval for NTP messages, from 10 to 17. Note units are in “log-base-two seconds,” or 2 to the power of
nseconds (NTP convention), meaning from 2 to the 10th (1024 seconds) to 2 to the 17th (131,072 seconds).