Configuration — PTP-Specific Steps
Confirm that:
The PTP Port Activity is enabled (check the Port Status on the PTP Status page under the
Advanced tab). If not, enable it from the Port Activity of the PTP Setup/Network page).
The clock is set to be a Master-Only clock (check the Clock Mode on the PTP Setup/Clock
page).
A valid IP address is currently being used (check the Ethernet Settings on the PTP
Setup/Network page).
When the PTP Module is set to be a Master Clock, the module will immediately attempt to
become the active Master Clock on the network (PTP Port State = Master). If it does, it will start to
transmit PTP packets (even if SecureSync is not yet synchronized).
There are several reasons why the PTP Module may not become the active Master Clock, or
may not be broadcasting the correct time, even if it is set to be a Master Clock:
a.
If using any reference other than self for 1PPS, SecureSync will not become an active
Master Clock until the Time Figure of Merit (TFOM) value of the system is less than 15. After
first going into sync after power-up, it may take a minute or two for the Time Figure of
Merit (TFOM) value to fall to an acceptable level. The current Time Figure of Merit
(TFOM) value is available in the Time Properties panel under the Advanced tab on the
Status page.
b.
PTP uses the TAI timescale to transfer time. Many timing references communicate time in
the UTC timescale. UTC is offset from TAI by a small amount which changes every time a
leap second occurs. The TAI to UTC Offset is part of the PTP Specification and must be
provided to a Master Clock. If no active reference can provide that information, the off-
set must be provided by the Host. The TAI to UTC Offset can be set from the
MANAGEMENT/OTHER/Time Management page (while setting the GPS to UTC Offset).
c.
The PTP protocol also provides for the transfer of Leap Second information. If the active
time reference does not provide Leap Second information, it must be added by the user
through the MANAGEMENT/OTHER/Time Management page. If this is not done, the PTP
network will have the incorrect UTC time after a leap second event.
d.
If there are multiple multicast Master Clocks on the network, the PTP Module uses the Best
Master Clock (BMC) algorithm specified in the PTP Specification to decide whether or
not to become the active Master Clock. The BMC algorithm selects the Best Master Clock
on the network from the following criteria:
i.
The BMC algorithm first selects the clock having the higher Priority1 parameter (a
lowest value means a higher priority).
SecureSync User Reference Guide 481
APPENDIX
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