3Com Switch 8800 Advanced Software V5 Configuration Guide

1066 CHAPTER 85: NTP CONFIGURATION

Figure 313 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.

■ 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 - server; 5 - broadcast or multicast; 6 - NTP control message; 7 - reserved for

private use.

■ Stratum: an 8-bit integer indicating the stratum level of the local clock, with

the value ranging from 1 to 16. The 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 and cannot be used as a reference clock.

■ Poll: 8-bit signed integer indicating the poll interval, namely the maximum

interval between successive messages.

■ Precision: an 8-bit signed integer indicating the precision of the local clock.

■ Root Delay: roundtrip delay to the primary reference source.

■ Root Dispersion: the maximum error of the local clock relative to the primary

reference source.

■ Reference Identifier: Identifier of the particular reference source.

■ Reference Timestamp: the local time at which the local clock was last set or

corrected.

■ Originate Timestamp: the local time at which the request departed the client

for the service host.

LI VN Mode Stratum Poll Precision

0 7 15 23 31

Root delay (32 bits)

Root dispersion (32 bits)

Reference identifier (32 bits)

Receive timestamp (64 bits)

Transmit timestamp (64 bits)

Authenticator (optional 96 bits)

Reference timestamp (64 bits)

Originate timestamp (64 bits)