Sticky Clients Not Roaming Correctly/SmartRoam.

Summary

When to use Smartroam feature on Zone Director/Unleashed.

Question

When should I use SmartRoam?

Customer Environment

Apple or other Sticky clients, high density, need for load balancing 

Root Cause

Some clients do not roam even if they are physically moved to a new location. Not all clients have roaming aggressiveness setting to fine tune roaming. Apple devices are reported to cling to the AP they first learn an SSID on.

Troubleshooting Steps

Usually triggered by client reports of not roaming, troubleshoot from ZD Administer/Diagnostics and enable Client Association and 802.11 components, then enter that client MAC in the focus box.

Collect debug logs soon after the client reports not roaming or disconnect/reconnect, and analyse Log.txt from collected ZD debug .zip file.  Determine client behaviour from log msgs, correlated to reported behaviour.

Background:

In a multi-AP environment, a client will always be looking for the best AP to connect to. It will remain connected to its current AP and roam to an adjacent AP once the signal level falls below a certain threshold. This behaviour ensures best possible performance at all times.

To achieve this, a client must be doing background scanning to learn about its environment. Frequency of this background scan can determine the roaming behaviour. Certain clients such as Windows clients allow roaming aggressiveness to be tweaked. "High" setting will make the client to perform background scanning more often to learn about available APs to connect. While the "Low" setting will make the client to do less frequent scanning. This setting can be found under the wireless adapter properties.

Unfortunately this tweaking is not readily available on all client types. For example, various smartphones and Apple clients do not provide this setting to encourage roaming.

For these type of clients, it is obvious to look towards infrastructure for help. Ruckus has added firmware support to disconnect a client if its signal falls below user definable threshold. This feature is called SmartRoam. With this feature there will be an explicit disassociate message to kick-off the client.

Resolution

Here is how to set this up from the ZD CLI:

This is a per-SSID setting as illustrated above. "smart-roam" parameter takes values from 1 to 10.
These are called roam factor, and they map to a RSSI value in dB as per the list below:

There will be an explicit disconnect event under the ZD logs in case this is triggered.