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Time synchronization
Summary
Both levels provide important and critical functions to an overall system that is being used to
control a plant's processes. System events can be generated from either the hardware side
(level 1) or from the supervisory side (level 2). Therefore, time synchronization between the
two network levels also needs to be coordinated, ideally, using the same source. This
mitigates against messages and events being mishandled, regardless of where they are sourced
from.
About time protocols
Simple Network Time Protocol (SNTP) is a proper subset of Network Time Protocol (NTP),
which uses the same packet format. As a subset, SNTP gets time from an NTP server, but
does not run complex filtering and control algorithms to extract the best time from multiple
sources and precisely set the local clock increment rate. SNTP only measures round-trip-delay
and sets the local clock when it drifts beyond internal limits.
Time protocols and Microsoft Windows
All supported Microsoft Windows operating systems use NTP. Each domain controller in a
Windows Server 2003 or 2008 domain, by default, is an NTP server. The Active Directory
provides a hierarchical time infrastructure. Each system added into the Active
Directory/domain synchronizes time with a time source in the domains hierarchy.
About setting up time synchronization in your Experion LX control system
Because the default Windows NTP implementation is not set up for the tolerances needed for
control systems, Honeywell recommends that you use the NTPConfig tool to configure time
synchronization on your Windows nodes. The NTPConfig tool corrects the tolerance
deficiencies and converts the Active Directory default settings to be compatible with control
system requirements. To overcome the tolerances, parameters are updated to maintain more
stringent time synchronization.
If your control system is integrated with a Windows domain, it is recommended that you use
the domain controller as the time source for all the clients within the domain (this is the
default setting). As domain controllers are typically not on a network that is accessible to the
control system itself, the controllers within the process control should be configured to get
their time from an Experion server that has been set up as an NTP server acting as a
secondary NTP server, which gets its time from the domain controller.
Time protocols and time servers for Experion LX controllers
The C300 uses SNTP or PTP to attain the time, but includes its own proprietary ability to
adjust the clock increment rate to that of the time source so that fewer actual adjustments
(bumps) are necessary (similar to the functionality of NTP).
When plant-wide correlation of C300 DI-SOE is required, PTP must be provided.
Honeywell 2017
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