H3C SR6600-X Configuration Manual page 129

Figure 43 Operation procedure of the Request_Response mechanism
Master clock
t1
t4
Figure 43 shows an example of the Request_Response mechanism in two-step mode.
1. The master clock sends a Sync message to the member clock, and records the sending time t1.
Upon receiving the message, the member clock records the receiving time t2.
2. After sending the Sync message, the master clock immediately sends a Follow_Up message that
carries time t1.
The member clock sends a Delay_Req message to calculate the transmission delay in the reverse
3.
direction, and records the sending time t3. Upon receiving the message, the master clock records
the receiving time t4.
4. The master clock returns a Delay_Resp message that carries time t4.
After this procedure, the member clock collects all four timestamps and obtains the round-trip delay to the
master clock by using the following calculation:
[(t2 – t1) + (t4 – t3)]
•
The member clock also obtains the one-way delay by using the following calculation:
[(t2 – t1) + (t4 – t3)] / 2
•
The offset between the member and master clocks is obtained by using the following calculations:
(t2 – t1) – [(t2 – t1) + (t4 – t3)] / 2
•
[(t2 – t1) – (t4 – t3)] / 2
•
Peer Delay
The Peer Delay mechanism includes the following modes:
Single-step mode:
•
t1 is carried in the Sync message, and no Follow_Up message is sent.
The offset between t5 and t4 is carried in the Pdelay_Resp message, and no
Pdelay_Resp_Follow_Up message is sent.
Two-step mode:
•
t1 is carried in the Follow_Up message.
t4 and t5 are carried in the Pdelay_Resp and Pdelay_Resp_Follow_Up messages.
Member clock
Timestamps
known by
member clock
t2 t2
t1, t2
t3 t1, t2, t3
t1, t2, t3, t4
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