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I'm consulting for a customer who has problems when roaming vofi handset between rooms separated by very thick walls and metal doors. The handset tends to be sticking to the first AP even if the signal is weak and there are clear drops in the voice stream. After a while it either decides to roam to the stronger AP and sometimes the call is dropped.
The APs are Cisco 1131 and the handsets are Cisco 7921 both on the newsest IOS firmware. The handsets are operating on 802.11a only and APs have very little chanel overlap. The handset typically sees 4 APs. Authentication is EAP-FAST over Cisco WDS. The plan is to go to LWAPP and the Airespace switch platform which might solve this. But we want to be sure so we don't t risk carrying over a general problem to the new platform.

We've tried to tune the Tx pwr down to a minimum to force the client to roam faster. That didn't help.

I've not yet done packet analysis. We already have AirMagnet Laptop Analyzer but cant see to get a grip with it on this problem. I'm are considering to get the AirMagnet VoFI analyzer to get a clearer view of where the problem lies: with the client, the AP RF or is it the authentication. I doubt it is with the call manager.

I'm looking for best practices for this scenario and pointer to what to look for.

Thanx

Delayed roaming is one of the major complaints I get from customers. Mostly they expect their 802.11 client to jump to the strongest RSSI value without regard to the quality of the current connection.
It sounds as if this is causing you real problems with this customer.
If I were troubleshooting this I would begin by understanding exactly what parameters and the values of those parameters that cause the client to roam. It is retransmission rate, data rate, error rate a combination of all the above and others? EXACTLY what does the client use to make its roaming decision?
Roaming is always a client decision. The only way you can influence that is to understand the client parameters that cause roaming, and adjust the parameters. After that you can modify the RF environment to have the conditions that create a client roaming event converge at the physical location where you want the client to roam.
You may need some tools to verify the RF environment to be able to adjust it to meet the client roaming requirements.
Best,
NovellRed

I'll throw a few things out there on this one, but without analyzing the actual traffic, it may be hard to tell what is going on for sure.

1. Is the SSID "hidden"? I've read that can mess with roaming clients.

2. Probably more important, have all the settings on the 7921's been checked? Roaming is on the client... I doubt its a problem with the WDS since FSR (association) should come after the phone already authenticated to the new AP.

Regards

I agree with both of you. Unless there is a major RF problem the client is the source of the problem. RSSI > -65 dBm and SNR >= 25db so RF looks fine. I will start looking into the client setup in detail even if we have done a check that the parameters are corresponding to the Cisco recommendations

The note on hidden SSID was interesting. Saving the clinets from probing will make the roaming process shorter. I checked my Airmagnet traces and yes the Voice SSID is hidden. Broadcasting the SSID will be the first parameter I'll attempt to change. I'll be back with an update.

Thanks for your input

Another note on this one...

Instead of turning the power down on the APs, try turning off the lower rates. It should force clients that are trying to stretch the boundary of the signal to shift quicker, but stay at a high rate.

Not sure if it will help...my guess is it's something on the client.

Good luck, and let us know the outcome.

Good stuff. I'll share my findings later.