probe-backoff

Defines the length of timeout for probing and sets criteria for CNA’s response to a timeout for probes with an active-measurement group.

probe-backoff [ trigger <time> ] [ wait <delay> ]
 
no probe-backoff
 

• time--number of seconds to wait for a prefix to respond to probing; range: 1 through 31556736
• delay--number of seconds to wait after a timeout has been triggered before resumption of probes; range: 0 through 31556736

Must be in active-measurement group configuration mode (config-engine-active), which requires privileged-level access.

Use once.

timeout--3600

delay--0

Use the probe-backoff command to define the length of time the CNA am-scheduler process should wait for a response to before it stops probing an unreachable or non-responsive target over an individual link, and the length of time the am-scheduler process should wait to resume probing that target again.

The probe-backoff command sets values which will apply only to active measurement targets that are associated with the active-measurement group. Trigger and wait times for probes that are not in a group are set by the active-measurement probe-backoff command.

You can set either or both (or none) of the values. Any value that you do not set when the command is added to the configuration will revert to the default. Entering the command without specifying a value is the equivalent of the no form of the command, which also reverts the values to their defaults.

You should be careful not to set the trigger interval smaller than the timeout value in the probe configuration. This will cause probing to be suspended after a single packet times out.

The trigger time should also take into account the number of probe failures that define a blackout (a user-configured number; see the outage-detection active-probe command). The default trigger time assumes a very low probing rate. The trigger time should be at least as large as the configured number of probe failures multiplied by the time between individual probes. You may want to set it larger than this calculated value to accommodate periodic fluctuations in prefix activity.

NOTE: If you set delay to 0 (the default value), the am-scheduler process will not wait any length of time before resumption of probing after a timeout has been triggered, effectively turning off the probe-backoff feature.

See Chapter 4: Server-Based Measurement of the CNA Basic Monitoring Guide.