Nokia 7210 Configuration Manual page 290

System Management
Figure 28
When the IEEE 1588v2 standard is used for distribution of a frequency reference, the
slave calculates a message delay from the master to the slave based on the
timestamps exchanged. A sequence of these calculated delays contains information
about the relative frequencies of the master clock and slave clock, but also includes
a noise component related to the PDV experienced across the network. The slave
must filter the PDV effects to extract the relative frequency data and then adjust the
slave frequency to align with the master frequency.
When the IEEE 1588v2 standard is used for distribution of time, the 7210 SAS
calculates the offset between the 7210 SAS time base and the external master clock
time base based on the four timestamps exchanged. The 7210 SAS determines the
offset adjustment, and between these adjustments, it maintains the progression of
time using the frequency from the central clock of the node. This allows time to be
maintained using a Synchronous Ethernet input source even if the IEEE 1588v2
communications fail. When using IEEE 1588v2 for time distribution, the central clock
should, at a minimum, have the PTP input reference enabled.
Figure 29
290
PTP Slave Clock and Master Clock Synchronization Timing
Computation
Master
38
40
42
44
t1
Sync
46
48
Follow_up (t1)
50
52
54
Delay_req
56
t4
58
60
Delay_resp (t4)
62
shows the logical model for using PTP/1588 for network synchronization.
© 2021 Nokia.
Use subject to Terms available at: www.nokia.com
7210 SAS-M, T, R6, R12, Mxp, Sx, S Basic System
Slave
40
42
44
O = Offset = Slave - Master
46
48
D = Delay
50
t2 t1, t2, t3, t4 Are Measured Values
52
t2 - t1 = Delay + Offset = 51 - 44 = 7
t4 - t3 = Delay - Offset = 57 - 56 = 1
54
Delay = ((t2 - t1) + (t4 - t3))/2 = 4
56 t3
Offset = ((t2 - t1) - (t4 - t3))/2 = 3
58
O D
60
62
64
Configuration Guide
OSSG732
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