Operation Manual – NTPH3C S7500 Series Ethernet Switches Chapter 1 NTP Configuration1-2Note:The accuracy of a clock is determined by its stratum, which ranges from 1 to 16. Thestratum of the reference clock ranges from 1 to 15. The accuracy descends with theincreasing of stratum number. The clocks with the stratum of 16 are in unsynchronizedstate and cannot serve as reference clocks.1.1.2 Working Principle of NTPThe working principle of NTP is shown in Figure 1-1.In Figure 1-1, The Ethernet switch A (LS_A) is connected to the Ethernet switch B(LS_B) through their Ethernet ports. Both of them have system clocks of their own, andthey need to synchronize the clocks of each other through NTP. For ease ofunderstanding, suppose that:z Before the system clocks of LS_A and LS_B are synchronized, the clock of LS_Ais set to 10:00:00am, and the clock of LS_B is set to 11:00:00am.z LS_B serves as the NTP time server, that is, the clock of LS_A will besynchronized to that of LS_B.z It takes one second for a packet sent by one switch to reach the other.IP networkIP networkIP networkIP networkLS_A LS_B10:00:00 am 11:00:01 am10:00:00 amNTP message 10:00:00 am 11:00:01 am 11:00:02 amNTP messageNTP messageNTP message received at 10:00:03 am1.3.2.4.LS_ALS_ALS_ALS_BLS_BLS_BFigure 1-1 Working principle of NTP
