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Configuration Guide - Device Management

CloudEngine 8800, 7800, 6800, and 5800 V200R002C50

This document describes the configurations of Device Management, including device status query, hardware management, Information Center Configuration, NTP, Synchronous Ethernet Configuration, Fault Management Configuration, Energy-Saving Management Configuration, Performance Management Configuration, Maintenance Assistant Configuration, and OPS Configuration.
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NTP Implementation

NTP Implementation

In Figure 4-1, the NTP client and server are connected. They are independent clock systems, and synchronize their clocks through NTP.

The parameter settings and synchronization are as follows:

  • Before the NTP client and server synchronizes their system clocks, the NTP client's clock is set to Ta and NTP server's clock is set to Tb.

  • The NTP server functions as the NTP clock server, with which the NTP client needs to synchronize its clock.

  • Assume that the precision between the system clocks on the NTP client and server is 0 (total precision).

Figure 4-1 NTP implementation

The system clock synchronization process is as follows:

  1. The NTP client sends an NTP request to the NTP server at T1. The request packet carries the timestamp T1, which is the time the packet leaves the client.

  2. The request packet reaches the NTP server at T2. The NTP server processes the packet, and sends an NTP reply packet at T3. This reply packet carries T1, T2, and T3.

  3. The NTP client receives the reply packet at T4.

Through the preceding interaction, the NTP client obtains four time parameters: T1, T2, T3, and T4. Assuming that the clocks of NTP client and server are precise, the time difference between the clocks of NTP client and server can be calculated using the following formula. The time difference is the time that the NTP client needs to be adjusted byt.

  1. Calculate the time (Delay) for sending an NTP packet from the client to server.

    Delay = [ ( T4 - T1 ) - ( T3 – T2 ) ] / 2

  2. Calculate the time difference (Offset) between the clocks of client and server.

    At T4, for example, the clock of server is T3 + Delay. The Offset is calculated as follows:

    T4 + Offset = T3 + Delay

    That is, Offset = T3 + Delay - T4 = T3 + [ ( T4 - T1 ) - ( T3 - T2 ) ] / 2 – T4 = [ ( T2- T1 ) + ( T3 – T4 ) ] / 2

The NTP client adjusts its own clock based on the Offset to synchronize clock with the server.

NOTE:

In the preceding description, the clocks are precise. However, there may be time difference between the clocks of client and server. Therefore, RFC 1305 defines complicated algorithms for NTP to ensure clock synchronization precision.

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Updated: 2019-03-21

Document ID: EDOC1000166632

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