Ntp Architecture - H3C SR6600-X Configuration Manual

Figure 26 Basic work flow
The synchronization process is as follows:
1. Device A sends Device B an NTP message, which is timestamped when it leaves Device A. The
time stamp is 10:00:00 am (T1).
2. When this NTP message arrives at Device B, Device B adds a timestamp showing the time when
the message arrived at Device B. The timestamp is 11:00:01 am (T2).
3. When the NTP message leaves Device B, Device B adds a timestamp showing the time when the
message left Device B. The timestamp is 11:00:02 am (T3).
4. When Device A receives the NTP message, the local time of Device A is 10:00:03 am (T4).
Up to now, Device A can calculate the following parameters based on the timestamps:
The roundtrip delay of the NTP message: Delay = (T4 – T1) – (T3 – T2) = 2 seconds.
•
• Time difference between Device A and Device B: Offset = ((T2 – T1) + (T3 – T4)) /2 = 1 hour.
Based on these parameters, Device A can be synchronized to Device B.
This is only a rough description of the work mechanism of NTP. For more information, see the related
protocols and standards.

NTP architecture

NTP uses stratums 1 to 16 to define clock accuracy, as shown in
represents higher accuracy. Clocks at stratums 1 through 15 are in synchronized state, and clocks at
stratum 16 are not synchronized.
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Figure 27. A lower stratum value