Before a PTP slave server can begin to synchronize with an upstream PTP master clock, it must receive PTP Announce messages. Before Announce messages are received and the master clock is selected, all other PTP messages received by the PTP slave are ignored.
The Announce messages contains data advertising the master clock type, accuracy and priority levels. The Announce message is used by the Best Master Clock algorithm to determine the most accurate master clock on a PTP network.
If a PTP sync module expects to receive an Announce messages, but does not do so, it outputs a warning message:
2016-12-21 11:47:19.652778: warning: failed to receive Announce within 12.000 seconds
Refer to Failed to Receive Announce Messages.