Ntp Message Format - H3C S5500-EI series Operation Manual

Operation Manual – NTP
H3C S5500-EI Series Ethernet Switches

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
0 1
LI VN
Figure 1-2 Clock synchronization message format
Main fields are described as follows:
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.
VN: 3-bit version number, indicating the version of NTP. The latest version is
version 3.
Figure 1-2.
4 7
Mode Stratum
Reference identifier (32 bits)
Reference timestamp (64 bits)
Originate timestamp (64 bits)
Receive timestamp (64 bits)
Transmit timestamp (64 bits)
Authenticator (optional 96 bits)
15
Poll
Root delay (32 bits)
Root dispersion (32 bits)
1-4
Chapter 1 NTP Configuration
23
Precision
31