set timemgmt

Purpose

Configures time source management settings.

Required permissions

For Digi products with two or more users, permissions must be set to
s-time-source=read to display time source management settings, and to s-time-source=rw to display and configure them. See set permissions for details on setting user permissions for commands.

Syntax

Configure time source management settings

set timemgmt [adjust_threshold=(seconds, 0 - 300)]
[recovery_state={on|off}]

Options

adjust_threshold=seconds

The Time Adjustment Threshold. This is a value in seconds that defines a range around the current time value maintained by the device. If a time update is received from a best-ranking (smallest-value) time source and the new time is within that range, the device's time is not changed. However, if the new time falls outside the defined threshold range, the device's time is updated immediately using the new time value.

The Time Adjustment Threshold value can range from 0 to 300 seconds. The default is 60. For example, if the configured threshold is 60 seconds, the device's time will be updated using a new time value that is 60 seconds or more different than the device's current time value. If the new time value differs from the device's current time by less than 60 seconds, the device's time is not updated using that new time.

The Time Adjustment Threshold is useful in limiting the amount of drift that will be tolerated before the device's time is updated using a new sample. An appropriate value should be selected with consideration for the reliability of the time sample sources.

In the case of NTP/SNTP server sources, the latency, round-trip timing and reliability of the network connection (between the device and the server) also should be considered.

For example, if the communications path between device and server involves a cellular network connection, the performance and behavior characteristics of the cellular network should be taken into account. In a cellular network, intermittent packet delays are possible in either the transmit or receive direction (or both). Frequently these delays are asymmetric, such that the delay is greater in one direction than in the other.

In such conditions, the round trip timing (of the request/reply) skews the time sample adjustment to determine the time value to use for the device. Therefore configuring an aggressively small (short) threshold value may cause the device to adjust its time frequently and unnecessarily, such that the time value “jumps” forward or backward as a consequence of asymmetric packet delays.

recovery_state={on|off}

The state of the Enable Lost Time Source Recovery setting. If multiple external time sources are available and configured, either by the set clocksource command or the Time Source Settings in the web interface, normally only the best-ranking (smallest value) source will be used to maintain the device's time. If the best-ranking source stops reporting new time values, it is considered “lost."

on

Enables Lost Time Source Recovery, which allows one or more worse (higher value) ranking time sources to be consulted in an effort to obtain a fresh time value. This prevents the best-ranking configured time source from blocking time updates if that source stops providing acceptable time samples.

The interval of time that must pass for Lost Time Source Recovery to begin varies according to the best-ranking time source that is reporting a value. For a time source of type sntp (an SNTP server, set by set clocksource type=sntp), the missing sample update interval is three NTP/SNTP intervals configured for that time source, plus one minute. For a time source other than sntp, the missing sample update interval is 61 minutes. These interval values cannot be user-configured.

off

Disables Lost Time Source Recovery.

Example

Set the adjustment threshold to 5 seconds and enable lost time source recovery

#> set timemgmt adjust_threshold=5 recovery_state=on