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Wireless LAN Roaming FAQ

[ Edited ]

The purpose of this FAQ is to address some of the most common questions and misconceptions that keep coming up in roaming related discussions in the UniFi forum. Also, it will hopefully serve to complement @UBNT-cmurphy's "Fast Roaming on UniFi" blog post. In case you don't have access to it, here's how to sign-up for beta: https://help.ubnt.com/hc/en-us/articles/204908664-How-To-Signup-for-Beta-Access

 

WLAN Roaming FAQ

 

What is roaming?

Simply put, roaming is the act or process by which a client device transitions from one cell (BSS) to another.

 

Is roaming a feature of the infrastructure (APs, controller, etc.)?

No. In the 802.11 standard (a.k.a Wi-Fi), roaming decisions are left to the client device and does not specify any criteria for determining when and where to roam to. All the wireless infrastructure can do is leverage standards-based and/or proprietary mechanisms to try to influence client device roaming behavior and maybe provide for reduced roaming times. But that doesn't always work well.

 

How does a client device decides when and where to roam?

Different vendors use different criteria differently. Most of them take into account received signal strength, data rates (PHY rates), frame retry rates, and other metrics in their roaming algorithms. More often than not, roaming criteria isn't properly documented if at all. In the consumer space, iOS devices are the best documented ones.

Here's the link to Apple's iOS roaming KB: https://support.apple.com/en-us/HT203068

 

What roaming times are acceptable?

Whatever suits the intended application. If client devices are mostly used for web browsing, streaming content, email, etc. then even a roaming delay of a couple of seconds or more would be acceptable and sometimes even unnoticeable to the user. On the other hand, if the primary use is for realtime and delay-sensitive applications like voice, then roaming times should be kept under 150ms.

  

What could be the cause of poor roaming experience?

The single most common cause of poor roaming experience is a bad wireless network design or lack thereof. This includes too high of a Tx power setting on APs, not enough cell overlap, incorrect data-rate settings, ect. Good roaming begins at layer 1 (RF). Also, features like MinRSSI (as currently implemented) and bandsteering can also cause issues. Another thing that must not be overlooked is buggy client device drivers which isn't uncommon. Lastly, using WPA2-Enterprise (802.1X/EAP) severely increases roaming times.

 

What is 802.11r (Fast BSS Transition)?

It is an amendment to the 802.11 standard which mostly addresses authentication and key management optimizations in order to significantly reduce roaming times in networks with 802.1X/EAP (WPA2-Enterprise) implemented. It eliminates the need for the client device to authenticate against the RADIUS server every time it roams from one cell to another, effectively bringing roaming times closer to those of a WPA2-PSK network and thus below the 150ms mark.  

 

Is UniFi's Fast Roaming the same as 802.11r? 

No. UniFi's Fast Roaming "feature" is an optimization done in the background that doesn't require client device support. Ubiquiti hasn't made any specifics public but, in a properly designed and configured WPA2-PSK network, roaming delays should be negligible. 

 

Do I need 802.11r (Fast BSS Transition)? Should I enable it if/when available?

The answer to both questions will almost always be "no". Unless of course you need to support realtime/delay-sensitive applications (e.g. voice) on a WPA2-Enterprise wireless network or your application/client vendor recommends enabling it. Another very important fact is 802.11r requires client devices that either support or are aware of it. Older/outdated devices (e.g. barcode scanners, printers) will have issues connecting to a wireless network with this functionality enabled, so it can end-up creating more issues for you.

 

But isn't 802.11r supposed to solve my roaming problems?

No. If you are experiencing roaming issues or excessive delays with a WPA2-PSK network, the root of the problem will most likely be some of the reasons listed above having to do with design and (possibly) configuration, faulty client drivers, and/or environmental issues none of which 802.11r can do anything about.

 

What about 802.11k (Radio Resource Management) and 802.11v (Wireless Network Management)?

The mechanisms introduced with these two amendments help client devices make better roaming decisions which can help improve roaming experience in a properly designed and implemented network. Neither will do anything to fix the most common causes for poor roaming which lie at layer 1 (RF) as explained above.

 

How about Zero Handoff?

Zero Handoff is an overhyped, largely misunderstood and misused buggy implementation of what is called a "Single Channel Architecture". It never came out of beta and it is only supported in the first generation of UniFi access points (e.g. UAP, UAP-LR) which no one should be buying/deploying today.

See herehere, and here for more information on what Zero Handoff is and how it works.

 

What can I do to improve or fix roaming in my business network?

As pointed out before, the best way to ensure a good roaming experience is by having a solid layer 1 (RF) design. It requires a good understanding of how Wi-Fi works and how client devices behave. That's what qualified WLAN consultants/engineers are for. Save yourself a lot of trouble and headaches by hiring one to help you.

 

But I'm a Home/SOHO user, what can I do to improve roaming?

Probably the best thing you can do is going with a solution/product intended for your use-case. That is to say AmpliFi, Eero, Orbi, Luma, etc. These tend to work reasonably well in home settings.

 

Omar

 Omar Vazquez - Consultant | Trainer
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Re: Wireless LAN Roaming FAQ

Excellent post - bookmarked!

When you receive a solution to your question/issue, don't forget to mark your thread as solved and to give kudo's to the people who have helped you out!

Having wifi problems? Take a look here first: https://help.ubnt.com/hc/en-us/articles/221029967-UniFi-Debugging-Intermittent-Connectivity-Issues-on-your-UAP
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Re: Wireless LAN Roaming FAQ

Indeed a great post.  It sounds like you really don't think Ubiquiti products belond in a SOHO environment.  I personally love the product and interface compared to anything else I've seen.

 

Perhaps you would be willing to offer some additional FAQ tips for those of us who want to tackle using UniFi in a SOHO environment?

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Re: Wireless LAN Roaming FAQ

@EricE Thanks!

 

@matthewlegrand You're right. I don't think UniFi belongs in a SOHO environment or at least that it should be the first option to consider. Of course that is unless you have some specific (more advanced) needs that would require it.  

 

Omar

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Re: Wireless LAN Roaming FAQ

Roaming type rkv, is present for all new Apple machines, samsung galaxy s5 and never. It is standard for corporate. Is not ridiculous playground for hippies. In my enterprise environtment, it is in 80% machines.

So please do not underestimate problem absence rkv roaming.

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Re: Wireless LAN Roaming FAQ

[ Edited ]

Unifi works great in a SOHO environment. I installed Unifi gear with a lot of family and friends who complain about the crappy WiFi supplied by the ISP. I always prefer a solution with cables -if possible- in relation to Mesh networks. Also a lot of the mentioned consumer product aren't available in the Netherlands.

 

Except for the above, great FAQ, but leave it a bit more objective Man Wink 

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Re: Wireless LAN Roaming FAQ

I found this very interesting but it leaves me with more questions...

 

I have tried UAP (legacy) with Zero Handoff and indeed it was not very successful.

 

Will the UAP ac Lite solve roaming problems where the client devices are reluctant to leave a weak signal?

Is the controler software different in some way, where do I find more about 'fast roaming'?

 

I have applications that are awkward wifi areas but will mostly be covered by two or three APs. But we are handling mobile clients that have wifi devices over which we have little control and we know are very inclined to hold onto a signal even when it has become too weak to offer any reliable communication.

 

Can the newer Unifi devices and 'fast roaming' help solve our problem independent of this client behaviour?

 

Any guidance will be greatly appreciated.

 

AF

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Re: Wireless LAN Roaming FAQ


@AFIFL wrote:

 

 

Will the UAP ac Lite solve roaming problems where the client devices are reluctant to leave a weak signal?


No. Like I pointed out in the FAQ above, roaming is a client device decision. Unless you have direct control over the client device (roaming thresholds, etc.) the only thing you can do is try to force it to roam by enabling MinRSSI and tweaking minimum supported data rates for example. Keep in mind that neither of these methods will guarantee a "good" roaming decision on the client device's side. Also, MinRSSI can create more issues than it solves, specially for delay-sensitive applications like VoWLAN.


AFIFL wrote:

 

Is the controler software different in some way, where do I find more about 'fast roaming'?


No. UniFi's "Fast Roaming" feature is enabled by default and since it is an optimization done in the background there's nothing for you to configure. See the following posts/threads for more information on it:

https://community.ubnt.com/t5/UniFi-Beta-Blog/Fast-Roaming-on-UniFi/ba-p/1756830

https://community.ubnt.com/t5/UniFi-Wireless-Beta/Discussion-Fast-Roaming-on-UniFi/m-p/1756855/highl...

https://community.ubnt.com/t5/UniFi-Wireless/Fast-Roaming/m-p/1761163


AFIFL wrote:

 

 

Can the newer Unifi devices and 'fast roaming' help solve our problem independent of this client behaviour?


No. Again, roaming decisions are made by the client device. So unless you have control over the specific client device all the infrastructure can do is try to influence/encourage it to roam. 

 

Omar

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Re: Wireless LAN Roaming FAQ

Thank you, your advice and links are much appreciated.

AF

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Re: Wireless LAN Roaming FAQ


OmarVR wrote:

 

@matthewlegrand You're right. I don't think UniFi belongs in a SOHO environment or at least that it should be the first option to consider. Of course that is unless you have some specific (more advanced) needs that would require it.  


Can you please go into more detail about why you don't think Unifi is suitable for a SOHO environment, especially for the "prosumer" segment where the person maintaining the network understands and is prepared to deal with the fact that this product takes a bit more work, but has benefits that you don't typically get in retail wifi gear.

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Re: Wireless LAN Roaming FAQ

[ Edited ]

Dear, @OmarVR, thanks for you job to us.

 

When I use FR will it be reset and reassign DHCP address for wifi client or not during move from one AP to other?

 

Best regards,

Viktor.

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Re: Wireless LAN Roaming FAQ

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Re: Wireless LAN Roaming FAQ

[ Edited ]

@wayner92 wrote:

OmarVR wrote:

 

@matthewlegrand You're right. I don't think UniFi belongs in a SOHO environment or at least that it should be the first option to consider. Of course that is unless you have some specific (more advanced) needs that would require it.  


Can you please go into more detail about why you don't think Unifi is suitable for a SOHO environment, especially for the "prosumer" segment where the person maintaining the network understands and is prepared to deal with the fact that this product takes a bit more work, but has benefits that you don't typically get in retail wifi gear.


Sure. The issue here isn't whether UniFi could work well in many Home/SOHO environments out there, but whether it is the best and/or most cost-effective solution for this kind of networks or not.

 

The rationale behind a lot of people choosing to go with UniFi for their Home/SOHO networks seem to stem from the notion that it will definitely do a better job than a consumer-oriented solution. After all, since it is a business-grade WLAN system then it should follow UniFi will do a better job than any consumer-oriented product. It is only logical, right?  Problem is that notion seldom holds true regardless of whether we are talking about UniFi, Cisco, Aruba, etc.  "Best"/"better"/"good" can only be defined in the context of the specific application or use-case in point. So what's best for case "A" might not necessarily mean it will be the best option (or even a good one) for case "B". Specially when the requirements of those usecases differ greatly.

 

Now, will a couple or more UniFi  APs do a better job than your typical Wi-Fi router (or router + extender combo)? Most likely yes. But often the improvements experienced aren't because of UniFi per se but the distributed nature of the system. Meaning having radios closer to wherever the client device happens to be. That's the reason why more and more residential Wi-Fi solutions are implementing the same approach. 

 

AmpliFi, Eero, Luma, OnHub just to name a few are based on a similar architecture and are designed specifically for the kind of use and applications found in the vast majority of homes and small offices with simplicity in mind. That means they keep things simpler and easier to manage and their testing is focused on making sure your Chromecasts, Xbox, Sonos, Apple TVs, Nests, etc., etc. work well with their solution. Some add things like parental control and similar functionality that are valuable for a residential usecase.

 

UniFi does provide more granularity/functionality by comparison but also introduces a lot of additional complexity as well. And whether those could be considered "benefits" will depend on the specific usecase. Also, keep in mind that having more knobs to tinker with when not really needed more often than not means a bigger chance of breaking something rather than improving it. That's one of the reasons I always tell people to follow the K.I.S.S. (keep it stupid simple) principle when it comes to Home/SOHO Wi-Fi.

 

So if you just need reliable connectivity and decent performance for the typical Home/SOHO application and don't require support for more advanced things like RADIUS authentication and VLANS, then the kind of products I've mentioned before will be a better fit. On the other hand, if more advanced functionality is needed and/or you are someone who enjoys playing with more intricate systems geared towards business use (SMB or Enterprise) then UniFi will be a better fit.

 

Omar

 

 

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Re: Wireless LAN Roaming FAQ


@VGusev2007 wrote:

Dear, @OmarVR, thanks for you job to us.

 

When I use FR will it be reset and reassign DHCP address for wifi client or not during move from one AP to other?

 

Best regards,

Viktor.


IP address is preserved.

 

Omar

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Re: Wireless LAN Roaming FAQ

[ Edited ]

OmarVR wrote:

IP address is preserved.

 

Omar


Dear @OmarVR nice to read that. I have many UAP-LR / UAP (and I want to have much more UNIFI AP) and I have old logistic devices like printers/win CE device and so on without 11.r support. They reassign ip from my dhcp when move from AP to AP (e.g. 192.168.10.10 -> start move -> 0.0.0.0 (plus winCE drops DNS cache during this Mad5) -> ask for dhcp again ->  192.168.10.10 again -> finish move) and my apps crash because of this. Please update FAQ for that if DHCP will stable during move.

 

It will be good for me with FR if I update to UniFi 5.4.11 Controller + update firmware with UniFi firmware 3.7.37 for UAP, UAP-LR? After that I will create a new WAN group (non default) + VLAN for that.

 

BEST REGARDS,

Viktor.

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Re: Wireless LAN Roaming FAQ

Thanks Omar. That makes sense. 

 

Here in Canada where we have basements and the most logical place to put your networking gear like your ISPs modem and your router is in the basement where your cable and/or phone enter the house. This is especially the case if your house has Ethernet cabling that terminates in this location. But this is not a good place for a WAP since it is a corner of your basement. So I think it makes a ton of sense to separate your router from your WAPs. That is what lead me to Unifi - I was using additional routers as WAPs around my house and wanted a better solution and you don't see that many pure WAPs for consumers these days. 

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Re: Wireless LAN Roaming FAQ


@VGusev2007 wrote:

OmarVR wrote:

IP address is preserved.

 

Omar


Dear @OmarVR nice to read that. I have many UAP-LR / UAP (and I want to have much more UNIFI AP) and I have old logistic devices like printers/win CE device and so on without 11.r support. They reassign ip from my dhcp when move from AP to AP (e.g. 192.168.10.10 -> start move -> 0.0.0.0 (plus winCE drops DNS cache during this Mad5) -> ask for dhcp again ->  192.168.10.10 again -> finish move) and my apps crash because of this. Please update FAQ for that if DHCP will stable during move.

 

It will be good for me with FR if I update to UniFi 5.4.11 Controller + update firmware with UniFi firmware 3.7.37 for UAP, UAP-LR? After that I will create a new WAN group (non default) + VLAN for that.

 

BEST REGARDS,

Viktor.


I think I'm understanding your situation better now. I strongly suggest you do a test run with your devices/applications and the latest stable controller and firmware to see if there's improvement.

 

Omar

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Re: Wireless LAN Roaming FAQ

One thing to consider however, is that if your house is wired with Cat5+, the consumer mesh networks can’t take advantage of that wiring.
For me, using the existing cat5 wiring and the clean look of Ubiquiti devices makes the effort worthwhile for home networking.
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Re: Wireless LAN Roaming FAQ

[ Edited ]

I strongly disagree about the SOHO and Zero Handoff part in the topicstart :

 

- Zero Handoff is what made me buy Ubiquiti UAP's about 3 years ago or so and it worked great in a a house with 3 floors!

In fact I am very disappointed to see it beeing dropped by Ubiquiti at one point and it's giving me a headache since the WPA KRACK crap started so I had to update the firmware to the latest version : UAP's reboot sometimes for no reason and then stay online for 20 days or just a couple of minutes... it's totally random!

I am almost at the point of reverting to the old firmware that was running before but then the security part will start bugging me Man Sad

 

- UAP's not for SOHO ?! HELL NO!

In the last three years or so there have been a very large amount of people buying UAP's and USG's or even the EdgeRouters for their (newly bought) homes and I think pretty much all of them have zero complaints Man Happy

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Re: Wireless LAN Roaming FAQ

I’m about to set up a network at home with USG, POE switch, cloud key, and IW-PRO x2; looking forward to it!
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