H3C Technologies H3C WX5500E Series Access Controllers User Manual
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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 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.