Protocols And Standards - H3C SR6600-X Configuration Manual

Figure 44 Operation procedure of the Peer Delay mechanism
Master clock
t1
t4
t5
The Peer Delay mechanism uses Pdelay messages to calculate link delay, which applies only to
point-to-point delay measurement.
the 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.
3. The member clock sends a Pdelay_Req message to calculate the transmission delay in the reverse
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 Pdelay_Resp message that carries time t4, and records the sending time
t5. Upon receiving the message, the member clock records the receiving time t6.
5. After sending the Pdelay_Resp message, the master clock immediately sends a
Pdelay_Resp_Follow_Up message that carries time t5.
After this procedure, the member clock collects all six timestamps and obtains the round-trip delay to the
master clock by using the following calculation:
[(t4 – t3) + (t6 – t5)]
•
The member clock also obtains the one-way delay by using the following calculation:
[(t4 – t3) + (t6 – t5)] / 2
•
The offset between the member and master clocks is as follows:
• (t2 – t1) – [(t4 – t3) + (t6 – t5)] / 2

Protocols and standards

IEEE 1588-2008, IEEE Standard for a Precision Clock Synchronization Protocol for Networked
•
Measurement and Control Systems
• IEEE P802.1AS, Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area
Networks
Member clock
Timestamps
known by
member clock
t2 t2
t1, t2
t3 t1, t2, t3
t6 t1, t2, t3, t4, t6
t1, t2, t3, t4, t5, t6
Figure 44 shows an example of the Peer Delay mechanism by using
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