Configuration using Web Based Management and Command Line Interface
4.5 The Switch menu
SCALANCE X-300 / X-400
240
Configuration Manual, 10/2014, C79000-G8976-C187-22
Synchronization mechanisms with transparent clocks
When calculating the actual message delay times over several network nodes, the time
required for processing a message in a transparent clock must also be taken into account.
This means that the transparent clock must calculate the time between receiving a message
at the input port and forwarding it at the output port and send this value to the slave. To this
end, there is a correction field in the PTP message in which the switches can make
appropriate entries. The slave takes this information into account in the calculation of the
message delay time.
How a transparent clock handles this correction information depends on the delay
mechanism that was configured. With the delay request response mechanism, there is an
end-to-end transparent clock, with peer delay mechanism, there is a peer-to peer
transparent clock.
End-to-end transparent clock
In the example shown, the time master sends a synchronization message. The time
Δ
TC
between receiving this message at the input port and forwarding it at the output port is
entered in the correction field of the follow-up message by the transparent clock. The time at
which this is sent t
0
is also received by the slave with the follow-up message and it can use
this as described above to make the necessary calculations.
