14.1.2
PTP Protocol details
Synchronization and management of a PTP system is achieved through the
exchange of messages across the communications medium. To this end, PTP
uses the following message types.
l
Sync, Delay_Req, Follow_Up
and
Delay_Resp
messages are used by
ordinary and boundary clocks and communicate time
-
related information
used to synchronize clocks across the network.
l
Pdelay_Req, Pdelay_Resp
and
Pdelay_Resp_Follow_Up
are used by
transparent clocks to measure delays across the communications medium
so that they can be compensated for by the system. Transparent clocks
and these messages associated with them are not available in IEEE
1588
-
2002.
l
Announce
messages are used by the best master clock algorithm in IEEE
1588
-
2008 to build a clock hierarchy and to select the grandmaster.
l
Management
messages are used by network management to monitor,
configure and maintain a PTP system.
l
Signaling
messages are used for non
-
time
-
critical communications
between clocks. Signaling messages were introduced in IEEE 1588
-
2008.
Messages are categorized as
Event
and
General
messages. Event messages
are time
-
critical in that accuracy in transmission and receipt timestamp
accuracy directly affects clock distribution accuracy.
Event messages:
l
Sync
l
Delay_Req
l
Pdelay_Req
l
Pdelay_resp
General messages :
l
Announce
l
Follow_Up
l
Delay_Resp
l
Pdelay_Resp_Follow_Up
General messages are more conventional protocol data units in that the data
in these messages is of importance to PTP, but their transmission and receipt
timestamps are not.
Management
and
Signaling
messages are members of the
General
message
class.
GEN3t
I3995-3.1 en HBM: public
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