PRISM MPI2-25 and MPX2-25 Media Analysis Platform User Manual
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As the PTP is locking, the slave clock will be adjusted, so the trace
may have large swings or jumps. As the system locks the Master to
Slave and Slave to master delays should converge on the same value.
This value represents the average network delay between the master
and slave for the traffic in both direction.
If the network delay is too unstable, then the PTP may never be able
to lock. This will appear as large variations on this trace.
o
Slave to Master Variation graph
: The master to slave variation, is
derived from the same data as the master to slave delay. The absolute
value of the changes in delay are filtered according to RFC1889 and
displayed. This display then shows a measure of the variation of the
network delay. A low value will indicate that a PTP slave will have
an easy time locking, a large value will indicate it may be
challenging for a PTP slave to get a good lock.
o
PTP Phase Lag graph
: The PTP phase lag is the error in the slave
clock phase as measured by the PTP timestamps. This value is used
to adjust the slave clock to drive the error toward zero.
It is the phase error of the phase locked loop, which controls the
slave clock. The phase lag is a reasonable estimate of how well the
PTP slave is locked to the master, however the phase lag does not
indicate if there is any asymmetry in the network.
