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PTP (Slave) Servo Configuration Parameters
Main Time Constant
The main time constant used by the PTP Servo (slave) algorithm, in seconds. A longer time constant
makes the oscillator frequency change more slowly and less responsive to changes in a network
environment, such as the temperature or the network delays. For networks with low packet delay
variation a short time constant (e.g., 30 sec) can be used. For networks with unknown or high traffic
load, a longer time constant (e.g., 300 sec) would be a better setting. A longer time constant requires a
more stable oscillator to be effective. For example, a time constant above 500 sec requires the
EdgeSync+ HP OCXO. The default value is 100 sec.
Startup Time Constant
The time constant used during the period of obtaining a preliminary synchronization (startup phase), in
seconds. If this field is set to 0 the main time constant will be used. This parameter can help to shorten
the synchronization time when a long main time constant is required. But values that are too short may
lead to unwanted oscillations which increase the total time required to synchronize and eliminate any
positive effects of shorter startup time constant. The default value is 0.
Quality Threshold
Defines the maximum allowed time variation in nanoseconds before the slave goes into holdover. The
time variation is based on a statistical measurement of time error between the source input time and
the slave’s formulated time, where the source input time is the GNSS or ToD + 1PPS input. The default
value is 1500 nsec.
Network Type
The Network Type selection is used to adjust the loop control algorithm behavior according to the
underlying network characteristics. There are three types of networks currently supported:
Unmanaged, Managed, and Full on-path.
“Unmanaged” selection is used for a network with unknown or unspecified packet delay and delay
variation or with packet delay distribution that may dramatically change its characteristics over time.
“Managed” selection is used for a network where the packet delay and delay variation distribution are
specified and that always has a distinct “floor”. That “floor” may vary over the time, but the distribution
limitations provided by the “floor” should still be present.
“Full on-path” selection is used along with G.8275.1 profile, where all network elements in the network
participate in PTP protocol.
Frequency Out
The syntonized frequency that will be output on the FREQ Out port on the EdgeSync Front Panel. The
valid options are 10MHz (default), 1.54MHz (T1 frequency) and 2.048 (E1 frequency).
SNTP
Besides PTP timing protocol, EdgeSync supports SNTP (Simple Network Time Protocol) for those
applications where very high precision (i.e., sub-microsecond accuracy) synchronization is not a
requirement. Many client devices and their operating systems synchronize to a NTP server. EdgeSync
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General