The state of 802.11r

802.11r or BSS Fast-Transition is a way of significantly increasing the speed of roaming in Wi-Fi environments. More specifically it’s an enhancement to the Wi-Fi standard that describes how to avoid having to perform a full WPA2 authentication when roaming to a new AP.

For the vast majority of clients Fast-Transition (FT) is no big deal. If a user is idly browsing the web, or their client is performing some background sync tasks, a roam from one AP to another isn’t something they notice.

Where it matters is when there are voip clients, or any application that doesn’t tolerate packet loss or high latency.

In an enterprise environment it’s common to use 802.1X authentication. This is quite a chatty affair, and it takes a bit of time. The hallowed figure often quoted for voip clients is to keep latency under 150ms. The process of roaming to a new AP and then performing 802.1X can take longer than this.

With FT, the network authentication part of the roam is reduced dramatically. However, it does need to be supported by the client and network.

Like many standards, there were some elements open to interpretation. Some network vendors required a client to support 802.11r in order to connect to the network, others did not. But with our Aruba network it was initially necessary for all clients to support 802.11r before you could switch it on.

This has changed over time and most vendors have moved to a position of allowing clients that do and do not support FT to co-exist on the network.

Client support has been mixed. For example Apple’s iOS does support 802.11r but MacOS does not (at the time of writing) but happily coexists with it.

Windows 10 includes support, but this seems to be dependent on the Wi-Fi chipset and driver. Which brings me to the blunt message of this post.

In an Aruba OS8 environment, with a jumbled mix of clients, it’s not yet possible to enable 802.11r. I’ve just tried it and run into a couple of Windows 10 laptops that were no longer able to connect to the network. The symptoms observed were the EAP transaction with RADIUS timing out. The user experience was, of course, “the Wi-Fi is down”.

Ekahau Connect

One of the tools that’s made the most difference to my work with WiFi has to be Ekahau Site Survey (now known as Ekahau Pro) and it’s now better than ever. I’m just going to go straight for the exciting part. Ekahau Connect lets you plug your Ekahau Sidekick into your iPad for surveying and, yes, that is as lightweight and functionally glorious as it sounds. But there’s more…

Ekahau have turned what was one application, Ekahau Site Survey, into a suite that form Ekahau Connect. There’s Ekahau Pro – the Windows/Mac application that many WiFi professionals know and love. Ekahau Capture – Packet capture utility for the Sidekick. Ekahau Cloud – a cloud sync service, and Ekahau Survey – an iPad app used for surveying with the Sidekick.

To get the advantage of all this new goodness it’s pretty clear that you need a Sidekick. I found the Sidekick to be a worthwhile investment from the get go, but now I can connect my Sidekick to my iPad, it’s become something of a must have.

For surveying, for me, it’s transformative. The Sidekick with an iPad combination is lightweight with long battery life and much easier to operate on the move. Pan and zoom around the floor plan is so much smoother and easier on the iPad, and that really matters when you’re on your feet and also having to negotiate obstacles in your path.

I’ve been using ESS for the last few years and have always struggled to come up with a really satisfactory workflow for surveys. In part that’s because I’m often dealing with small academic offices (the offices are small, not the academics) which are not always easy to move around, and the doors all have aggressive auto-closers that try to eat my laptop. In short, I’m usually fighting piles of paper, books and doors, all while ensuring I’m being accurate with my location clicking on the floor plan. Even the lightest weight laptop starts to feel heavy after a while. I’ve been using a Lenovo Yoga, for the fold over touchscreen design and whilst it’s easier to carry around, it’s actually fairly hard work to operate because Windows and touch have never really gelled.

On the iPad it’s a different story. For a little while I’ve been playing with the beta of Ekahau Survey as the team beat back the rough edges (there really weren’t very many) and took on board feedback from everyone giving it a spin.

Using an iPad I can survey more quickly, make fewer errors that I need to correct, and keep going for longer. It’s a real productivity boost.

The workflow is pretty straight forward. Create your project in Ekahau Pro then export the project either to Ekahau Cloud or to the internal storage of your Sidekick. The latter option being particularly useful if surveying for a site where you don’t have internet access for your own device. The Ekahau team have talked a lot about how they ensure data isn’t lost if there’s a crash or the battery dies, by saving data to the iPad, the cloud service and the Sidekick.

From the moment I got my Sidekick I’ve wondered how long it would be before there was a packet capture utility… and now it’s here. I didn’t have advance information, it was just an obvious use case. Wireless packet capture under Windows has always been a slightly tricky task, Ekahau Capture and Sidekick make it really easy and the dual radios mean you can get complete (non-scanning) captures on two channels at the same time.

I’ve briefly mentioned Ekahau Cloud, but it’s worth exploring a little bit because it makes sharing projects easy. This is a big help for teams. It also means it’s possible for a team to work on different floors of the same building, and sync all that data back to the same cloud project.

I don’t want to neglect Ekahau Pro in this big update as it’s had more than just a new name. Quite a lot has changed under the hood. The visualisations are improved and I believe there’s also been some work done on improving the prediction algorithms.

Bottom line is if you’re already using Ekahau tools, especially if you already have a Sidekick, you’ll want to spring for this new suite so it’s worth putting together a case for management or your accountant to consider.

Professional tools – Ekahau

As I started to take up the mantle of Wi-Fi human for a university campus, it was mentioned that we had “the Ekahau laptop”. This turned out to be a woefully under powered old netbook with Ekahau Site Survey installed. Nobody knew how to use it. So I learned.

Fast forward a few years and I’m an Ekahau Certified Survey Engineer who’s designed and surveyed a lot of our campus using this tool.

Ekahau Site Survey is, as the name suggests, a survey tool. It’s also a Wi-Fi design tool. I’ve used it extensively for both tasks and it’s probably one tool I’d struggle to do without.

One of the strengths of ESS it’s relative simplicity. At the most basic level you import a floor plan, set a scale and then you’re ready to use this for predictive design work, or a real world survey.

Surveying is a matter of walking around a building, while clicking on your location on the floor plan. There’s a technique to this of course, but it really is just a matter of walking the floors.

To use Ekahau Site Survey as a design tool you’ll need to draw on walls, doors, filing cabinets and other attenuation areas as appropriate. Then you can place APs on the plan and ESS will show you what coverage can be expected.

What should be obvious about both predictive and survey data is the pretty visualisations generated by ESS will show you exactly what you’ve told it. If you put junk data into your predictive model by saying all the walls are drywall with a 3dB attenuation, your design isn’t going to work very well when it turns out you have 10dB brick walls. So it’s important to have some idea of the building construction and, ideally, have taken measurements.

Likewise with the survey side, if you’re inaccurate with your location clicking or walk 100m between clicks and force ESS to average the data over too large an area, you’ll get a result that’s not as useful.

In short, you do need to know how to use the tool – just like anything.

A quick mention of WiFi adapters. ESS works by scanning the selected WiFi channels (all available in your regulatory domain by default) and recording information and received signal strength of the beacons transmitted from access points. It’s necessary to have a compatible WiFi adapter that can be placed in monitor mode. Low cost options are available. If you give ESS two or three adapters it will spread the channel scan across these, allowing data to be gathered more quickly. ESS will also use the built in WiFi of your laptop to ping an IP or perform speed tests against an iperf server.

I started with a single USB interface, which I used to bash on door frames, before upgrading to a quick release (lego glued to the laptop lid) USB hub with three interfaces connected. This made the laptop lid too heavy and it would fall backwards.

To counter these first world problems, but also to allow for other interesting functionality, Ekahau made the Sidekick. It’s a neat box containing two dual band WiFi radios (802.11ac), a very fast spectrum analyser, processing capability and storage, and a built in battery.

For surveying Sidekick isn’t a necessity but it makes life much easier. The data gathered is more complete, the laptop battery lasts longer and the spectrum analyser capability turns ESS into a powerful troubleshooting tool.