This article contains information about the Citrix ADC monitor parameters Retries, Failure Retries and DownTime

Retries

By default, a Citrix ADC appliance requires a specific number of consecutive retry failures to mark the state of the service as DOWN. The possible value for the number of consecutive probe failures after which an appliance marks status of the service as DOWN, is in the range of 1 to 127. By default the value is 3.

For example, if you assume a TCP monitor with parameters as listed as follows, then the appliance checks the service every 10 seconds and after three consecutive probe failures or after three SYN packets are sent to the backend server with no response, the appliance marks the status of the service as DOWN.

Interval=10
Retries=3
Failure Retries=0

The status of the service is marked as DOWN after three consecutive probe failures.

• PF PF PF = The status of the service is marked as DOWN.
• PF PS PF = The status of the service is not marked as DOWN.

Where, PF indicates SYN packet or probe failures and PS indicates SYN packet or probe is succeeded.

Failure Retries

This optional parameter indicates the number of probes that must fail for a service to be marked as DOWN, out of the number specified for the Retries parameter. For example, if the Retries parameter is set to 10 and the Failure Retries parameter is set to 6; out of the 10 probes sent, at least 6 probes must fail if the service is to be marked as DOWN. The default value of 0 means that all the retries must fail if the service is to be marked as DOWN.

For example, if you assume a TCP monitor with parameters as listed as follows, then the appliance checks the service every 10 seconds and after three probes out of the five retries are sent to the backend server with no response, the appliance marks the status of the service as DOWN.

Interval=10
Retries=5
Failure Retries=3

Based on the settings given above, the status of the service is marked as DOWN after three probe failures out of the five:

• PF PF PF = The status of the service is marked as DOWN.
• PF PS PF PS = The status of the service is not marked as DOWN.
• PF PS PF PF PS = The status of the service is marked as DOWN after three probe failures out of the five retries, based on the Failure Retries parameter.

Where, PF indicates probe failures and PS indicates probe is succeeded.

Down Time

When the status of the service is marked as DOWN, the Citrix ADC waits for a specific period before probing the service again. This parameter is called DownTime 
and is expressed in milliseconds, seconds, or minutes. The default value is 30 seconds.  After the downtime, the Citrix ADC appliance sends the number of probes configured on the Retries parameter. 

LB monitor command reference