How Ntp Works - HP 5500 EI Series Configuration Manual

• The local clock of this Switch Series cannot operate as a reference clock. It can serve as an NTP
server only after it is synchronized.
• NTP supports access control and MD5 authentication.
NTP can unicast, multicast, or broadcast protocol messages.
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How NTP works

Figure 5 shows the basic workflow of NTP. Device A and Device B are connected over a network. They
have their own independent system clocks, which need to be automatically synchronized through NTP.
Assume that:
Prior to system clock synchronization between Device A and Device B, the clock of Device A is set
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to 10:00:00 am while that of Device B is set to 1 1:00:00 am.
Device B is used as the NTP time server, so Device A synchronizes to Device B.
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It takes 1 second for an NTP message to travel from one device to the other.
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Figure 5 Basic workflow of NTP
The synchronization process is as follows:
Device A sends Device B an NTP message, which is timestamped when it leaves Device A. The
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timestamp is 10:00:00 am (T1).
When this NTP message arrives at Device B, it is timestamped by Device B. The timestamp is
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1 1:00:01 am (T2).
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