Advanced roaming features

Disclaimer: I did not test all the below described features in a production network. Some features require support/feedback from the client itself which is not always there or clients are getting confused by enabling this features with a bad user experience as result. Always make sure to monitor the impact of your changes and test upfront as much as possible. Keep in mind that a good wireless infrastructure starts with a good RF design and multiple validation site surveys. These features can only help to further optimize.

There are quite a few features available on the AirOS controllers and access-points which are (indirect) related to roaming. Some of them are Cisco proprietary and some are based on industry standards, but all of them share the goal to use the RF as efficient as possible and positive influence the user experience.

For my CCIEW studies I created the list below with relevant features based on 8.0 version of AirOS code.

Feature Client support required Description
Rx SOP No Force clients to roam or leave the WiFi network by ignoring frames on the radio level with a certain signal strength.

Rx SOP Configurations are supported on AP1600, AP2600, AP2700, AP3500, AP3600, AP3700 and AP1550 only.

RSSI Low Check No Motivate clients to use another access-point or leave the WiFi network by denying clients with a certain signal strength to associate.
Optimized roaming No Motivate clients to use another access-point by disassociate clients with a certain signal strength.

Optimized roaming uses some of the values configured within the coverage hole detection mechanism.

Aggressive load balancing* No Clients are being motivated to use another access-point.

APs in local mode will send a code 17 (AP busy) message, with Flexconnect APs the client is being de-authenticated.

Band select No Motivate dual-band clients to use 5 Ghz instead of 2.4 Ghz by delaying probe responses on the 2.4 GHz.
Assisted roaming (802.11k)* Yes Inform clients about alternative APs to limit the need for active and passive scanning on the client when it wants to roam. After a certain amount of denied association responses the client will be allowed.

The prediction part of the Cisco implementation is not based on 802.11k and does not require client support.

Fast Transition (802.11r) Yes Introduces a concept of roaming where the initial handshake with the new AP is done even before the client roams to the target AP.
CCX Client Roaming Yes Provide CCXv4 enabled clients with roaming configuration parameters to direct influence the roaming behavior.

*: Because both load balancing and assisted roaming are designed to influence the AP that a client associates with, it is not possible to enable both the options at the same time on a WLAN.