H3C Technologies H3C S5120 Series Switches User Manual

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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

Mode

Stratum

Poll

Precision

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)

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.

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 from the client for the service

host.