Alcatel-Lucent 7210 SAS-D User Manual

System Management
7210 SAS D, E, K OS Basic System Configuration Guide Page 205
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 Figure 22. This figure illustrates the offset of the slave clock referenced to the best
master signal during startup.
Figure 22: PTP Slave Clock and Master Clock Synchronization
Timing Computation
Slave
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
O = Offset = Slave - Master
OD
40
D = Delay
OSSG644
42
44
46
48
50
52
54
56
58
60
62
64
Master
40
42
1t44
38
46
48
50
52
54
56
58
t2
60
62
t3
t2
Sync
Follow_up (t1)
Delay_req
Delay_resp (t4)

Alcatel-Lucent 7210 SAS-D Specifications

General

Brand	Alcatel-Lucent
Model	7210 SAS-D
Category	Switch
Language	English