Fast Roaming Setup

Unanswered Question
Aug 2nd, 2009


I have the following environment setup:

- 3 Aironet AP (AIR-LAP 1242AG) in Channel 1,6,11 of radio interface 802.11b/g/n

- 1 WLAN controller (WLC 2106)

- Laptop with Linux kernel 2.6.27

- Atheros TP-Link 54M Wireless CardBus Adapter (TL-WN510G)

- Security policies [WPA + WPA2][Auth(PSK)]

With these components, is it possible to gain the benefit of fast secure roaming (<100ms) for VoIP application? If not, what other components/configuration/policies are necessary?

Thanks in advance.

I have this problem too.
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dancampb Mon, 08/03/2009 - 05:43

There are a couple ways to get fast roaming but you're best bet is to use WPA2 with AES encryption. Part of the WPA2 spec is reauths using a PMK instead of doing a full authentication. Keep in mind using a PMK is not a required part of the spec so your client doesn't have to support it.

yokekhei1 Mon, 08/03/2009 - 20:19

Based on my understanding, my Linux client laptop can only support pre-authentication and PMK caching if an additional RADIUS server is setup.

Without RADIUS server, if I would like to configure my client to skip the authentication message and direct sending reassociation request to new AP while roaming, will this work for my Aironet AP and WLC? As I understand that WLC already contains the client entry in its database.

dancampb Tue, 08/04/2009 - 04:36

Yes, you will need a Radius server. The first time the client authenticates a full authentication will be done. Any time the client reassociates the auth will be handled by the PMK. The controller will cache the PMK but if you are using a security that doesn't have a fast roaming option the client will do a full authentication every time.


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