System Management
Basic System Configuration Guide 263
Figure 16: Ethernet Multicast Ports
The ordinary clock master, ordinary clock slave, and boundary clock allow for PTP operation
over both unicast IPv4 and multicast Ethernet at the same time.
The IEEE 1588v2 standard includes the concept of PTP profiles. These profiles are defined
by industry groups or standards bodies that define how IEEE 1588v2 is to be used for a
particular application.
Currently, three profiles are supported:
• IEEE 1588v2 default profile
• ITU-T Telecom profile for frequency (G.8265.1)
• ITU-T Telecom profile for time with full timing support (G.8275.1)
When an ordinary clock slave or a boundary clock receive Announce messages from one or
more configured peers or multicast neighbors, it executes a Best Master Clock Algorithm
(BMCA) to determine the state of communication between itself and the peers. The system
uses the BMCA to create a hierarchical topology allowing the flow of synchronization
information from the best source (the Grandmaster clock) out through the network to all
boundary and slave clocks. Each profile has a dedicated BMCA.
If the profile setting for the clock is ieee1588-2008, the precedence order for the best master
selection algorithm is as follows:
• priority1
al_0527
7750 SR
Boundary Clock
Port 1/2/1
Port 1/1/1 Port 1/3/1
Boundary Clock
Boundary Clock
Ordinary Clock
Slave
Ethernet Multicast LAN
Ordinary Clock
Master
End to End Transparent Clock
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