Configuration using Web Based Management and Command Line Interface
4.5 The Switch menu
SCALANCE X-300 / X-400
Configuration Manual, 10/2014, C79000-G8976-C187-22
241
If a message on the way to a slave is forwarded by other transparent clocks, each device
adds its time Δ
TC
to the content of the correction field of the follow-up message. When the
synchronization message arrives at the slave, the correction field contains the sum of all the
times required to process the messages in the transparent clocks. The device also handles
the delay request messages in the same way.
The slave corrects the message delay time by the value Δ
TC
or, with several transparent
clocks, by the sum of all the Δ
TC
values and can synchronize its time of day as described in
the section "Delay request response mechanism".
Peer-to-peer transparent clock
With the peer delay mechanism, each device calculates the delay time of a message to the
neighboring device for its ports. The transparent clock obtains the message delay time L1 to
the master, the slave obtains the value L2 for the message delay time to the transparent
clock.
The processing of the synchronization message by the transparent clock takes a time of Δ
TC
.
The transparent clock enters the sum of L1 and Δ
TC
in the correction field of the follow-up
message. The slave then adds the content of the correction field to the message delay time
L2 for the input port via which the synchronization message was received. In this way it
obtains the delay time of a message between master and slave.
If a message on the way to the slave is forwarded by several transparent clocks, each
transparent clock changes the content of the correction field of the follow-up message: The
message delay time to the neighbor via which the synchronization message was received,
and the time Δ
TC
for processing the message are added to the content of the correction field.
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