S
M1
S1
M2
S2
M3
S3
S
S
S
Boundary clock
switch
Transparant clock
switch
Grand master
clock
M
Grand master
clock
M
Boundary clock operation
Transparent clock operation
System 1
System 2
System 3
System 1
System 2
System 3
Figure 14.1:
Boundary clock versus transparent clock switch synchronization
mode
14.2.1
Switches using boundary clocks
Switches using boundary clocks have a built
-
in clock and they create separate
synchronization domains by segmenting the synchronization path from the
master clock to several slave clocks. As a result, systems downstream of a
boundary clock do not communicate PTP messages with the selected (grand)
master directly. Standard Ethernet messages are passed through the switch
while synchronization messages are used to synchronize the boundary slave
clock.
HINT/TIP
As boundary clock switches create their own internal clock, the overall stability
and/or accuracy of the grandmaster clock is no longer available for any of the
attached systems.
GEN3t
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