H3C SR6600-X Configuration Manual page 127

Figure 42 Clock nodes in a PTP domain
OC 1
Master port
Besides the three basic types of clock nodes, PTP introduces some hybrid clock nodes. For example, a
TC+OC has multiple PTP ports in a PTP domain. One port is the OC type, and the others are the TC type.
A TC+OC forwards PTP messages through TC-type ports and performs delay corrections. In addition, it
synchronizes time through its OC-type port. TC+OCs include these types: E2ETC+OC and P2PTC+OC.
Master-member/subordinate relationship
The master-member/subordinate relationship is defined as follows:
Master/Member node—A master node sends a synchronization message, and a member node
•
receives the synchronization message.
Master/Member clock—The clock on a master node is a master clock. The clock on a member
•
node is a member clock.
• Master/Subordinate port—A master port sends a synchronization message, and a subordinate
port receives the synchronization message. The master and subordinate ports can be on a BC or an
OC. A port that neither receives nor sends synchronization messages is a passive port.
Grandmaster clock
In Figure 42, all clock nodes are organized into a master-member hierarchy, where the grandmaster
clock GM operates as the reference clock for the entire PTP domain. Time synchronization is implemented
through exchanging PTP messages.
A GM can be manually configured, or it can be elected through the Best Master Clock (BMC) algorithm
by following this procedure:
1. The clock nodes in a PTP domain exchange announce messages and elect a GM by using the
following rules in descending order:
a. Clock node with higher priority 1.
Grandmaster clock
BC 1
TC 1
OC 2
OC 3
Subordinate port
TC 2
BC 2
TC 3
OC 4 OC 5
Passive port
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PTP domain
BC 3
TC 4
OC 6