Figure 2 Clock synchronization message format
Main fields are described as follows:
l 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.
l VN: 3-bit version number, indicating the version of NTP. The latest version is version 3.
l 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.
l 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.
l Poll: 8-bit signed integer indicating the poll interval, namely the maximum interval between successive messages.
l Precision: an 8-bit signed integer indicating the precision of the local clock.
l Root Delay: roundtrip delay to the primary reference source.
l Root Dispersion: the maximum error of the local clock relative to the primary reference source.
l Reference Identifier: Identifier of the particular reference source.
l Reference Timestamp: the local time at which the local clock was last set or corrected.
l Originate Timestamp: the local time at which the request departed the client for the service host.
l Receive Timestamp: the local time at which the request arrived at the service host.
l Transmit Timestamp: the local time at which the reply departed the service host for the client.
l Authenticator: authentication information.