Description

Glossary

RFCs

Publications

Obsolete RFCs

Description:

NTP version 0

NTP version 1

NTP version 2

NTP version 3

NTP version 4
This version adds support for the Autokey security protocol.

NTP version 3 message

LI, Leap Indicator. 2 bits.
This field is used to warn of an impending leap second.

Version. 3 bits.
NTP version number.

Mode. 3 bits.

Stratum. 8 bits.
Stratum level of the local clock.

Poll interval. 8 bits, signed.
The maximum interval between messages in seconds to the nearest power of two.

Precision. 8 bits, signed.
Precision of the local clock in seconds to the nearest power of two.

Root delay. 32 bits, signed fixed point.
The total roundtrip delay to the primary reference source, in seconds with the fraction point between bits 15 and 16. Positive and negative values are valid.

Root dispersion. 32 bits, signed fixed point.
The maximum error relative to the primary reference source in seconds with the fraction point between bits 15 and 16. Only positive values greater than zero are valid.

Reference clock identifier. 32 bits.
Used to identify the particular reference clock.

In the case of stratum 2 and greater (secondary reference) this is the IPv4 address of the primary reference host.

In the case of stratum 0 (unspecified) or stratum 1 (primary reference), this is a four byte, left-justified, zero padded ASCII string. While not enumerated as part of the NTP specification, the following are suggested ASCII identifiers:

Reference timestamp. 64 bits.
The local time at which the local clock was last set or corrected.

Originate timestamp. 64 bits.
The local time when the client sent the request.

Receive timestamp. 64 bits.
The local time when the request was received by the server.

Transmit timestamp. 64 bits.
The local time when the reply was sent from the server.

Authenticator. 0 or 96 bits.