Operation Manual – NTP
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 NTP Configuration
1-4
1.1.3 NTP Message Format
NTP uses two types of messages, clock synchronization message and NTP control
message. An NTP control message is used in environments where network
management is needed. As it is not a must for clock synchronization, it will not be
discussed in this document.
Note:
All NTP messages mentioned in this document refer to NTP clock synchronization
messages.
A clock synchronization message is encapsulated in a UDP message, in the format
shown in
Figure 1-2
Clock synchronization message format
Main fields are described as follows:
z
LI: 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.
z
VN: 3-bit version number, indicating the version of NTP. The latest version is
version 3.
z
Mode: a 3-bit code indicating the work mode of NTP. This field can be set to these
values: 0 – reserved; 1 – symmetric active; 2 – symmetric passive; 3 – client; 4 –