R3204P16-HP Load Balancing Module System Management Configuration Guide-6PW101

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This is only a rough description of the work mechanism of NTP. For more information, see RFC 1305.
NTP message format
NTP uses two types of messages: clock synchronization messages and NTP control messages. An NTP
control message is used in environments where network management is needed. Because it is not
essential for clock synchronization, it is not described in this document.
NOTE:
A
ll NTP messa
g
es mentioned in this document refer to NTP clock synchronization messa
g
es.
A clock synchronization message is encapsulated in a UDP message, in the format shown in Figure 54.
Figure 54 Clock synchronization message format
Main fields are described as follows:
• LI (Leap Indicator): A 2-bit leap indicator. When set to 11, it warns of an alarm condition (clock
unsynchronized); when 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 3.
• Mode: A 3-bit code that indicates the work mode of NTP. This field can be set to these values:
a. 0—reserved
b. 1—symmetric active
c. 2—symmetric passive
d. 3—client
e. 4—server
f. 5—broadcast or multicast