Figure 22: Ptp Slave Clock And Master Clock Synchronization - Alcatel-Lucent 7210 SAS-D Configuration Manual

two-step synchronization operation can be used, with the two-step operation requiring a follow-up
message after each synchronization message.
NOTE: The 7210 SAS-D ETR supports only two-step master port operation. All node types can
operate slave ports that receive from a one-step or two-step master port.
During startup, the PTP slave clock receives the synchronization messages from the PTP master
clock before a network delay calculation is made. Prior to any delay calculation, the delay is
assumed to be zero. A drift compensation is activated after a number of synchronization message
intervals occur. The expected interval between the reception of synchronization messages is user-
configurable.
The basic synchronization timing computation between the PTP slave clock and PTP best master
is illustrated in
master signal during startup.
7210 SAS D, E, K OS Basic System Configuration Guide
Figure 22. This figure illustrates the offset of the slave clock referenced to the best
Master
38
40
42
1 t 4 4
46
48
Follow_up (t1)
50
52
54
Delay_req
56
t2
58
60
Delay_resp (t4)
62

Figure 22: PTP Slave Clock and Master Clock Synchronization

Timing Computation
Slave
40
42
44
46
48
Sync
50
t2
52
54
56 t3
58
O D
60
62
64
System Management
O = Offset = Slave - Master
D = Delay
t1, t2, t3, t4 are measured values
t2 - t1 = Delay + Offset = 51 - 44 = 7
t4 - t3 = Delay - Offset = 57 - 56 = 1
Delay = ((t2-t1) + (t4 - t3))/2 = 4
Offset = ((t2 - t1) - (t4 - t3))/2 = 3
OSSG644
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