Nokia 7210 SAS-M - Page 288

System Management
288
7210 SAS-M, T, R6, R12, Mxp, Sx, S Basic System
Configuration Guide
3HE 16132 AAAB TQZZA Edition: 01
As part of the basic synchronization timing computation, event messages are defined
for synchronization messaging between the PTP slave clock and PTP master clock.
A one-step or two-step synchronization operation can be used; the two-step
operation requires a follow-up message after each synchronization message.
During startup, the PTP slave clock receives 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.
Figure 28 shows the basic synchronization timing computation between the PTP
slave clock and PTP best master; the offset of the slave clock is shown referenced
to the best master signal during startup.
Figure 28 PTP Slave Clock and Master Clock Synchronization Timing
Computation
Note:
• The 7210 SAS-M supports only two-step master port operation.
• The 7210 SAS-Mxp, 7210 SAS-R6, 7210 SAS-R12, 7210 SAS-Sx 1/10GE, and
7210 SAS-T support only one-step master port operation.
• All platforms can operate slave ports that receive from a one-step or two-step master
port.
Master Slave
Sync
Follow_up (t1)
Delay_req
Delay_resp (t4)
38
40
42
44
46
48
50
52
54
56
58
60
62
40
42
44
46
48
50
52
54
56
58
60
62
64
O = Offset = Slave - Master
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
D = Delay
t1
t4
t2
OD
OSSG732
t3