CCKM vs Mobility Groups - Roaming for Voice Clients

[tony.sangha]

Hi there,

I am looking at deploying wireless at our site for voice, I have a couple of questions regarding Roaming between APs and best way to acheive fast roaming for latency senstive voice and other applications.

According to Cisco SRND for Voice over Wireless (

http://www.cisco.com/en/US/docs/solutions/Enterprise/Mobility/vowlan/41dg/vowlan_ch5.html), it is recommended:

"Fast roaming algorithms include Cisco Centralized Key Management (CCKM)  and Proactive Key Caching (PKC). CCKM and PKC allow a WLAN client to  roam to a new AP and re-establish a new session key—known as the  Pairwise Transient Key (PTK)—between the client and AP without requiring  a full IEEE 802.1X/EAP reauthentication to a AAA/RADIUS server."

But let's say I used WPA/PSK for my WLAN and just rely on mobility information in the controller to perform the handover, would this still be best practice.

I have actually tested both and they work quite well, neither drops a call or experiences any degragation in voice quality. I suppose I am asking for a real world perspective and if I should adhere to the SRND on this one?

Many thanks

[George Stefanick · Accepted solution]

Hi Tony,

Great question BTW.

CCKM/OKC/PKC only comes into play when EAP is used. During the EAP process the PMK is seeded from the MSK. From the PMK, it is seeding the PTK. With no advance romaing in use as a client roams from AP to AP you would have to redo that process all over.

When you use PSK.. Your MSK is your PMK and there is no need to go back to the radius server for a new PMK. So your client and ap exchange this info.. no need for a radius server ..

Does this make sense?

[tony.sangha]

thanks George, that make's a lot more sense now!