Do i need a ZoneDirector for Wireless Roaming?

[marco_eichstet1]

Hi,

Do i need a ZoneDirector for Wireless Roaming?
One of my Customers need a Wireless Network for his Warehouse. There will be about 15 to 20 Wireless Barcode Scanner. The Scanner supports 802.11b/g/n.

I read there is no need for a ZoneDirector for Layer 2 Roaming because this is implemented in the 802.11 Protocoll. Is this true?

Please clarify.

Thanks.

Kind Regards
Marco

[koen_verbeeck]

Good reply Michael,

For the session credentials to be shared between access points, does 802.11r with 802.11k support needs to be enabled on the zonedirector or will enabling these features trigger an even faster (more seamless) roaming (for client devices that support these features) because of storing the PMKs at the zonedirector (PSK & 802.1x support) and also clients requesting neigboring reports from the access points. Will 802.11r trigger pre-authentication of the client devices with neigboring access points before re-association to these AP's?

Best regards,
Koen

[munish_munish]

Hi Koen,

In 802.11r Yes, the initial handshake with the new AP is done even before the client roams to the new AP( Fast Transition (FT). So the initial handshake tells the client and the AP to calculate the encryption keys in advance . These keys are than applied to the client and AP after the client request for re-association .

Thanks,

Munish

[primoz_marinsek]

I think the short answer to Marco Eichstetter question is NO. You don't need a ZD for roaming to work. The standard takes care of that not the ZD or any other control entity. Maybe in a single channel architecture things are different, but I don't actually know how things go there.

Then there is the consideration of authentication, which is a big factor here.

So when you have 2 APs configured with the same SSID and security parameters the client will decide to which one it is talking at any time. So if it's talking to AP1 and decides AP2 is better it will roam to that one and vice versa.

One thing that vendors do is help the client with the decision. This help is kind of 2 tier:

1. One is standard based with the implementation of 802.11k Radio Resource Measurement of Wireless LANs amendment. This however NEEDS to be supported on APs and client devices (STAs), otherwise it's useless

2. If 11k isn't supported a controller can gather data on an STA and if it thinks it has a better option for it it disassociates it thus forcing an association from an STA and hopefully the STA will connect to the same SSID but one advertised by a "nearer" AP with better signal. It's a hit and miss process.

The other thing is authentication that basically defines the speed of a roam as the STA needs to perform it every time it changes an AP association. These times can vary between 10ms to 300ms, depending on various things. The fastest way to do it now is by employing 11r as was discoussed by Koen and Munish, but again both nodes on a network need to support it.

So in the end, the answer is YES, you need a controller for roaming to work very fast, but you also need clients that support 11k & 11r and 802.1X must be employed.

[marco_eichstet1]

Hello Primoz Marinsek,

thanks for your detailed answer.
In my specific Case a Customer wants to deploy a wireless Network in his Warehouses. In the End there will be about 10 Wireless Bar Code Scanners. For my Customer its important that the Clients roam as "smooth" as possible. Unfortunatelly my Customer don't know which kind of Bar Code Scanner (Model, Vendor, etc.) he will get.

Someone of Ruckus reccomendet to use a ZD1106.
If i read the Information within this Topic it seems it whould be a good way to try roaming first without a ZD. If it works: Fine! If not: Lets try with a ZD.

Is this my way i should go?
If i understand right a STA have to support 11k to roam "smoothly". Is 11r just needed if i am using 802.1x or is it also good if i use a simple autonomous WPA2 Network?

Many Thanks!
Kind Regards
Marco

[primoz_marinsek]

To roam as smooth as possible scanners will have to support 11k, 11r and 1X will have to be deployed.

The second not so optimal, but still probably good option is too use a ZD and a static WPA2/AES key.

The last and the least optimal option is to use stand-alone APs configured with static WPA2/AES key.

Maybe start from the bottom and go up if needed.