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PTP Operational Overview
Five Basic PTP Timing Messages
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PRISM MPI2-10-MPX2-10 User Manual
Five Basic PTP Timing Messages
This section describes the five basic timing messages in a PTP system. Other messages
are present in some instances. For example, grant requests and responses appear in
unicast systems, and Type Length Value (TLV) management messages appear in SMPTE
ST2059 profile systems.
Announce Message
The Announce message is sent by the master to advertise its capability. This message
contains the clock quality and priority settings needed for the BMCA to evaluate which
device is the best master.
Sync Message
The Sync message is sent by the master and is used to measure the propagation delay
from the master to slave. The sync message may contain the timestamp indicating
when it was sent, or that time may be in the Follow-up message. The receiver must
timestamp the sync message upon receipt. These two time stamps are usually called t1
and t2 and provide the first delay measurement.
Follow-up Message
The Follow-up message is sent only in cases where the PTP network hardware is not
capable of inserting the timestamp or corrections into the Sync message. (See One-step
and Two-step Operation .)
Delay Request Message
The Delay request is sent by the slave. The time it is sent is noted by the slave but is not
included in the message. This time is usually called t3. When the delay request is
received by the master, the master time stamps the receive time. This timestamp is
usually called t4.
Delay Response Message
The Delay response is sent from the master to the slave. The response contains the t4
time stamp from when the master received the delay request. After the slave receives
the delay response, it has the second pair of time stamps needed to calculate the
second delay measurement of the slave to master delay.