H3c-technologies H3C WX5500E Series Access Controllers Instrukcja Użytkownika Pobierz pdf (Strona 18)

used in environments where network management is needed. Because NTP control messages are not

essential for clock synchronization, they are not described in this document.

A clock synchronization message is encapsulated in a UDP message in the format shown in Figure 6.

Figure 6 Clock synchronization message format

The main fields are described as follows:

• LI (Leap Indicator)—A 2-bit leap indicator. If set to 11, it warns of an alarm condition (clock

unsynchronized). If set to any other value, it is not to be processed by NTP.

• VN (Version Number)—A 3-bit version number that indicates the version of NTP. The latest version

is version 4.

• Mode—A 3-bit code that indicates the operation mode of NTP. This field can be set to these values:

{ 0—Reserved.

{ 1—Symmetric active.

{ 2—Symmetric passive.

{ 3—Client.

{ 4—Server.

{ 5—Broadcast or multicast.

{ 6—NTP control message.

{ 7—Reserved for private use.

• Stratum—An 8-bit integer that indicates the stratum level of the local clock, with the value ranging

from 1 to 16. Clock precision decreases from stratum 1 through stratum 16. A stratum 1 clock has

the highest precision, and a stratum 16 clock is not synchronized.

• Poll—An 8-bit signed integer that indicates the maximum interval between successive messages,

which is called the poll interval.

• Precision—An 8-bit signed integer that indicates the precision of the local clock.

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 103 104

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