Tektronix PRISM User Manual page 170

Application information
148
Top of the display:
PTP Lock: Shows the status of the PTP lock.
Grandmaster ID: Displays the reference Source and Domain.
PTP Time: Time of day derived from the PTP signals.
Profile: Shows the profile which has been selected in the reference
settings menu. This is not detected from the incoming PTP messages.
Resolution: The time increment for each bar on the display. Longer
graph settings collect data into larger bins to be displayed. This range and
resulting resolution are selected in the setting menu for PTP graphs.
Trace Types: There are four displays available. For each one, the Max, min
and average are show on the left, while the traces vs time is shown on the
right. The traces indicate the Max, and Min envelop, as well as the average
for each time bin. The time scale can be adjusted in the settings menu – touch
and hold the menu bar to access this menu. The data is logged for 7 days so
one can go back and look at long term trends.
Use the slider to move the displays up or down.
Master Slave Delay graph: This indicates the difference in the time
stamps for the PTP Sync messages which go from the master to the slave.
So this display will indicated effects of the downstream network delay
and adjustments made to the slave clock. After the slave is locked and
the timing is stable, then the perturbation on this graph are largely due to
network variations. Traffic will often cause some messages to be delayed
so then the maximum delay will increase.
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.
Master Slave 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.
PRISM Media Analysis Platform User Manual