Controller Based WLANs

How Does Handoff Assist Work?

Aruba Employee

In the RF optimization profile (Aruba OS 3.X or greater), the following settings related to handoff assist are present:

•     handoff-assist – enable/disable
•     low-rssi-threshold – minimum RSSI above which no deauth is sent
•     rssi-check-frequency – interval in seconds to sample RSSI readings
•     rssi-fallout-wait-time – seconds to wait with decreasing RSSI before deauth is sent to the client

Handoff assist must be enabled for the other settings to have any meaning.

If handoff assist is enabled and if an AP’s stations are active, then:

For every ‘rssi-check-frequency’ interval (measured in seconds), if the RSSI (Received Signal Strength Indication) is less than low-rssi-threshold for more than the rssi-fallout-wait-time, then the station will be deauthed, so that the station can associate to an AP with a stronger signal.  This can be useful if a particular client is ‘sticky’ in staying on an AP with a low signal RSSI when an AP with a stronger signal is closer.

Note:  Be careful with enabling the handoff assist feature.  Some clients will react adversely to being deauthed.  For instance, voice calls will drop if the phone is deauthed.  Also, if a particular client takes a long time to reauthenticate, then the deauth may negatively impact the station connectivity.

It is recommended to leave handoff assist disabled unless guided by the Aruba TAC in a specific case.

It is also recommended to thoroughly test the handoff assist feature with the appropriate client devices before enabling.

Default settings:

•     handoff-assist – disabled
•     low-rssi-threshold – 0
•     rssi-check-frequency – 0
•     rssi-fallout-wait-time – 0

Configuration:

(uw_master) #configure t
Enter Configuration commands, one per line. End with CNTL/Z

(uw_master) (config) #rf optimization-profile default
(uw_master) (RF Optimization Profile "default") #low-rssi-threshold 20
(uw_master) (RF Optimization Profile "default") #rssi-check-frequency 3
(uw_master) (RF Optimization Profile "default") #rssi-falloff-wait-time 4
(uw_master) (RF Optimization Profile "default") #handoff-assist
(uw_master) (RF Optimization Profile "default") #end

With these settings, for the rssi-check-frequency of 3 seconds, if the RSSI falls below 20 for a particular client, once the rssi-falloff-wait-time of 4 seconds is reached, then the client will be deauthed.

Show commands:

(uw_master) #show rf optimization-profile default

RF Optimization Profile "default"
---------------------------------
Parameter                              Value
---------                              -----
AP Load Balancing                      Disabled
AP Load Balancing Max Retries          8
AP Load Balancing User High Watermark  0
AP Load Balancing User Low Watermark   0
AP Load Balancing Util High Watermark  0
AP Load Balancing Util Low Watermark   0
AP Load Balancing Util Wait Time       0 sec
Station Handoff Assist                 Enabled         <-- Handoff assist enabled
Detect Association Failure             Disabled
Coverage Hole Detection                Disabled
Hole Good RSSI Threshold               20
Hole Good Station Ageout               30 sec
Hole Detection Interval                180 sec
Hole Idle Station Ageout               90 sec
Hole Poor RSSI Threshold               10
Detect interference                    Disabled
Interference Threshold                 100 %
Interference Threshold Exceed Time     60 sec
Interference Baseline Time             600 sec
RSSI Falloff Wait Time                 4 sec            <-- rssi-falloff-wait-time
Low RSSI Threshold                     20                <-- low-rssi-threshold
RSSI Check Frequency                   3 sec         <-- rssi-check-frequency

show ap monitor stats ap-name <ap name> mac <client/AP bssid>
     -- look in the handoff assist section of the output

Version history
Revision #:
1 of 1
Last update:
‎07-06-2014 09:54 PM
Updated by:
 
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