topic Do i need a ZoneDirector for Wireless Roaming? in Wireless Questions and Best Practices

Do i need a ZoneDirector for Wireless Roaming?

marco_eichstet1 — Mon, 15 Dec 2014 19:15:23 GMT

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

Re: Do i need a ZoneDirector for Wireless Roaming?

michael_brado — Mon, 15 Dec 2014 19:38:17 GMT

In my experience, barcode scanners run Telnet based applications that are very
sensitive to time delays and dropped packets. Using only standalone APs means
the scanners will have to re-authenticate with every roam. Having a ZoneDirector
allows for the cached client session credentials to be shared between APs and
allows for more seamless roaming, especially for VoIP and Scanner usage.

Re: Do i need a ZoneDirector for Wireless Roaming?

marco_eichstet1 — Mon, 15 Dec 2014 19:49:22 GMT

Hi Michael,

thanks for your Reply.
Ok. So if i understand right Roaming without ZD is working... more or less. It depends on the Client.

If my customer need a better (or even perfect) Roaming Experience he should use a ZoneDirector. Correct?

Is the statement true that Roaming is (in a simply) way implemented in the 802.11 Standard?

Thanks & Kind Regards
Marco

Re: Do i need a ZoneDirector for Wireless Roaming?

michael_brado — Tue, 16 Dec 2014 01:27:25 GMT

Hi Marco,

The fastest client re-association is facilitated by ZoneDirector managing client
sessions between Access Points under its control. Without a ZoneDirector, the
scanner is dropping from one AP, and performing an entire new connection to the
next AP, including another DHCP request, and will result in a few lost packets by
the scanner telnet application. If these dropped packets are enough to freeze the
application or cause it to lose session with the server will have to be evaluated,
but for best results, the ZD is a valuable piece of the solution.

Re: Do i need a ZoneDirector for Wireless Roaming?

koen_verbeeck — Tue, 16 Dec 2014 08:33:08 GMT

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

Re: Do i need a ZoneDirector for Wireless Roaming?

monnat_systems — Tue, 16 Dec 2014 16:09:23 GMT

Hi Marco, The 802.11 standard explicitly places control of wireless connection establishment in the hands of clients by defining various logical services and breaking implementation out between clients and access points."

Even if controller is there you shall keep in mind that roaming will NOT always be smooth due due to the fact that decision and how fast to roam is taken care by STA or client.

Hope this helps.

Re: Do i need a ZoneDirector for Wireless Roaming?

munish_munish — Tue, 16 Dec 2014 17:19:36 GMT

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

Re: Do i need a ZoneDirector for Wireless Roaming?

primoz_marinsek — Wed, 17 Dec 2014 08:38:34 GMT

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.

Re: Do i need a ZoneDirector for Wireless Roaming?

marco_eichstet1 — Wed, 17 Dec 2014 09:32:04 GMT

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

Re: Do i need a ZoneDirector for Wireless Roaming?

primoz_marinsek — Wed, 17 Dec 2014 09:39:38 GMT

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.

Re: Do i need a ZoneDirector for Wireless Roaming?

koen_verbeeck — Wed, 17 Dec 2014 10:38:28 GMT

Hey Marco,

The goal of 802.11r & 802.11k is that when using 802.1x authentication for the first time, this authentication process will happen between the client device (supplicant), Zonedirector (authenticator) and RADIUS server (authentication server) and can take up to a few seconds depending where it is located, once successfully authenticated, the RADIUS (AAA) server will send the MSK = PMK to the Zonedirector which will be stored there and forwarded to all APs in the same mobility domain that request it. The 4-way handshake (deriving session keys) will happen between the AP the client is connected to and the client device itself. Now when the client device is roaming to another AP (and i think the client can even auth to other AP's before making a roaming decision) in the same mobility domain, the client will authenticate to the Zonedirector instead of the AAA server & re-associate with the new AP. The 4-way handshake will occur between the new AP and the client device. The client roaming time will be reduced from a few seconds to around 50ms. The 802.11k part is that clients who support this standard are able to request a neighbor report of the access point it is connected to. The AP will respond with a neighbor report containing following information on the top 8 neighboring AP's: SSID, channel #, PHY type, BSS capabilities, mobility domain, ect... The neighbor report empowers client devices with info to make the smartest roaming decision. Without 802.11k clients will learn neighbor AP information from probe responses

Guys, please correct me if i am wrong on this.
br.
Koen

Re: Do i need a ZoneDirector for Wireless Roaming?

marco_eichstet1 — Wed, 17 Dec 2014 11:42:04 GMT

Hi,

Sorry for the question again. I hope i am not too annoying. ;)

I read at "support.apple.com":
"11k" is for quickly identify nearby APs available for roaming. It doesn't matter if i am using static WPA2 or 802.1x.
"11r" streamlines the authentication Process using a Feature called FT and allows STA to associate with APs more quickly. Depending on WiFi-Hardware Vendor, FT works with static WPA2 (PSK) and 802.1x.

On "theruckusroom.net" i read 11r is just needed if i am using 802.1x, because the authentication Process needs his time. This Statement is the same like you (Koen and Primoz Marinsek) described.

Because my Customer don't have an IT-Staff. The IT-Staff is in fact one Person who manages the IT besides. I'm thinking to use DPSK (WPA2). Maybe he should look for Bar Code Scanner who supports 11k.

Thanks.
Marco

Re: Do i need a ZoneDirector for Wireless Roaming?

primoz_marinsek — Wed, 17 Dec 2014 14:32:43 GMT

Yes, 11k doesn't care about your authentication method.

Definitely the customer should buy a scanner that supports 11k, 11r and 11w. These things last for years and they should be future proof.

My suggestion is still the same. Start at the bottom of my last post and work your way up if needed.

Re: Do i need a ZoneDirector for Wireless Roaming?

marco_eichstet1 — Wed, 17 Dec 2014 15:39:34 GMT

Ok. Thanks!

Re: Do i need a ZoneDirector for Wireless Roaming?

john_d — Wed, 17 Dec 2014 16:51:23 GMT

Note that even on WPA2-PSK networks, my iOS devices start showing that they're using 802.11r FT to roam. Renegotiating WPA2-PSK is certainly faster than 802.1x and making it to a RADIUS server and back, but it still takes time.

Re: Do i need a ZoneDirector for Wireless Roaming?

nick_wollman — Wed, 27 May 2015 01:09:41 GMT

why does my zd 1100 not have an ft roaming option? or is that also dependent on the ap? my 1200 has it and im using r600s on it but only 7343s on my 1100.

Re: Do i need a ZoneDirector for Wireless Roaming?

michael_brado — Wed, 27 May 2015 23:43:04 GMT

Nick, the Fast BSS Transition WLAN option was introduced in 9.8 release. What version firmware are you running on your ZD1100?

Re: Do i need a ZoneDirector for Wireless Roaming?

nick_wollman — Thu, 28 May 2015 04:07:32 GMT

9.8. But that brings me to another point. I was looking at the release notes for 9.10 and I saw that the 7962 access point was not supported anymore. What does that mean exactly? I have a couple of those and I'd still like them to work when I update. Also my zone director 1100 reports a whole bunch of useful information such as users roaming from one AP to the next and AP join requests and heartbeats lost and stuff like that. My newer zone director 1200 only reports when rogue APs are detected and that's pretty much it. Do the new software updates make them report less stuff?

Re: Do i need a ZoneDirector for Wireless Roaming?

michael_brado — Mon, 01 Jun 2015 22:33:43 GMT

Product Marketing has End of Lifed the 7962 b/g and a/n 64mb RAM AP that served well since 8.0 version code.
New 802.11ac capable APs may not have all capabilities enabled in initial releases, but are being implemented.
To recognize/report Rogue APs for example, requires background scanning, and be sure that Rogue detction
is enabled.

https://support.ruckuswireless.com/answers/000001261

Re: Do i need a ZoneDirector for Wireless Roaming?

mitchell_axtell — Mon, 01 Jun 2015 23:07:46 GMT

The log settings changed in more recent firmware to show warning and critical events only, but it's easy to change this. Under Configure > System > Log Settings, click the "Show More" option and save. That will show the user roaming and other entries.