THE BLOG ★ Ramblings on WiFi & stuff.

♻︎ Today’s Quality Linkage

"Integrity and the WLAN Profession” WLPC session by @samuel_clements is a “must watch” for any WLAN engineer.

Building networks where the sun don't shine. @bmroute doing some cool Wi-Fi stuff in the netherworld.

Is there a need for a Spectrum Policy within the Enterprise? by @JustDoWiFi. I can totally see the need for this especially in critical environments like hospitals.

Understanding OFDM CWNE #10 @RickMurphyWiTS posts on OFDM are great.

AiRISTA to acquire Ekahau RTLS Not the Wi-Fi side (whew), but still, big news.

Aruba Visio Stencils Updated stencils. And they work in OmniGraffle too!

COOL TOOL: Netool - Pocket sized  network tester and analyzer First batch of beta units are coming out. Looks to be pretty nice.

Want to clean up India? Turn trash into free Wi-Fi Now THAT's an interesting concept. Socially engineered Wi-Fi.

NASA Releases New High-Resolution Earthrise Image Oh, my stars. 😳

Your Letters Helped Challenger Shuttle Engineer Shed 30 Years Of Guilt What a story. This poor guy was on the right side of history and no one knew.

802.11ax: "Next Gen Wi-Fi" changes all the rules...

Chuck Lukaszewski, from Aruba, talks at the Wireless LAN Professionals Conference about what's coming after 802.11ac. Well, it's a lot. So much about how we understand Wi-Fi to work is going to be turned on its head. Two-way MU-MIMO, infrastructure control/influence on clients, SMALLER channels, and more.

This is a must watch for anyone involved in wireless.

And here's a link to ALL the videos from WLPC. So many great sessions to watch.  

​♻︎ Today’s Quality Linkage

Announcing the Ekahau Master Wi-Fi Certification Jussi from Ekahau just announced this at WLPC. Pretty excited about this new program!

SSID Overhead, Now There's an App for that! WLPC is just full of firsts! @RevolutionWiFi announced an app version of his SSID Overhead calculator built by @RAdzima. Great tool for determining if your SSID count is causing any appreciable effect on your WLAN. Also, great for proving to the customer that 10 SSIDs is not a good thing. 👍

Engineers achieve Wi-Fi at 10,000 times lower power This seems like a very interesting option for IoT. It's all just "in the lab" at the moment, but I see potential. 

WiFi Channel Simulator by CWNE Rick Murphy This is a fantastic tool to visualize channels in 2.5/5Ghz. How many 80Mhz channels are available with, and without DFS? This will show you. Want to visualize for a customer why you shouldn't use overlapping channels (anything other that 1, 6, 11) in 2.4? This will show you. Luv!

Apple: an iPhone Backdoor Would Be Reused by China, Russia, and the US It's about what the Gov't is gonna ask for in the future. Oh, and EVERY OTHER COUNTRY as well.  

802.11ah Emerges to Connect the Internet of Things Old things have become new. 900MHz is being positioned to be the savior of the IoT Apocalypse. 

Designing Wi-Fi Networks for High Capacity. @JussiKiviniemi speaks at BICSI Winter 2016 Conference It's a video. 

What do "your" WiFi clients support? CWNE #150, Mike Albino, has created an online database of wireless clients and their capabilities. In this post Mike shows various ways to get that data from probe requests. This is a great resource for anyone in Wi-Fi. 

Asus lawsuit puts entire industry on notice over shoddy router security Uhg. This is why we can't have nice things. 😕

How Wireless Works  CWNEs Rick Murphy and Devin Akin have a new site that offers resources on wireless. Also, online training to learn Wi-Fi in-depth. Looks great. 

Airport Experiment Shows That People Recklessly Connect to Any Open WiFi Hotspot Personally, I ALWAYS use a VPN when on a public WLAN. Even an encrypted one. But, that's just me. ¯\_(ツ)_/¯  

A tense prequel fully explores Back To The Future’s terrorist backstory Cuz, who doesn't wish Doc Brown was bad-to-bone?

WLPC, here I come!

Estimated reading time: 1 minute, 24 seconds. Contains 280 words

 

Well, it's that time of year again - Wireless LAN Professionals Conference (WLPC). This is the 3rd (U.S.) conference, and my 3rd as well. I look forward to this gathering of Wi-Fi geeks all year. I tell anyone who asks about learning wireless - if you can only go to ONE conference - this is the one.

My first WLPC was in 2014 in Austin, TX, and other than following WLAN pros on Twitter, I knew no one. I was overwhelmed at the knowledge, and people, I had access to. I got to listen in on conversations with people like Keith Parsons, GT Hill, Devin Akin, Andrew Von Nagy, Chuck Lukaszewski, and others.

I was a total fish out of water. I had just gotten my CWNA a few months before, but I really didn't know how far I would go. This conference was the impetus to start my blog, get involved in the WLAN community, and set a goal of achieving CWNE.

I was encouraged by all the people I met. People like me, who were relatively new to the wireless thing, and those who were well entrenched. Meeting other 'newbies' was encouraging, because I wasn't the only one who felt insecure in their Wi-Fi proficiency. Meeting the 'Pros' was encouraging because they were welcoming and open to sharing their knowledge and expertise with those of us that were new.

I encourage all WLPC first timers to get in the thick of it. Make an effort to get to know people, ask questions, listen in, and get involved. Push aside any timidity you may have, because the folks at WLPC are more than willing to welcome you in and share the knowledge.

​♻︎ Today’s Quality Linkage

When is Wi-Fi blocking justified? by Peter Thornycroft

How Levi’s Stadium Delivered 10 TB of Wi-Fi for the Super Bowl Webinar from Chuck "I'll NEVER be on the Twitter" Lukaszewski. Don't miss this one!

Ruckus Tackles In-Building Cellular Problem Hmm. Interest peaked. For more on CBRS (3.5 GHz) read Ruckus' blog.

WLPC TenTALK by Martin Ericson: VoFi Phones and DFS Channels Things to consider.

This is how wi-fi actually works by @jimvajda Short and to the point.

802.11 Packet Capture Skillz To Pay The Bills by @WirelesssGuru

Engineering the wireless hospital: Mobility and connectivity Good read from the Wi-Fi Alliance.

CWNP overview of DFS and here's the FCCs document on DFS Client Devices

The Hummingbird Effect: what does the wine press have to do with astronomy? Science + History = Kewl!

The IT Crowd: Moss Introduces Jen To The Internet Such a great show. This is one of my faves scenes

DFS implications for hidden networks and roaming

UPDATE: See the comment below by Andrew Von Nagy. It clarifies what I said about hidden SSIDs and DFS.

 

I'm a huge advocate of using DFS channels in most medium to large deployment scenarios. But, you should always validate your channel plan and make sure it doesn't cause issues with you WLAN. By that I mean verify that your devices actually do support DFS. It’s possible certain devices support DFS, but not ALL DFS channels. Checking manufacturer documentation, Google, or site like clients.mikealbano.com can help you figure that out.

Case in point: Hidden SSIDs. Most wireless folks recommend against using hidden SSIDs. It doesn't provide any security, requires more work to connect devices to, and some NIC drivers don't like hidden networks and won't, or have trouble, connecting to them.

There are practical reasons to hide an SSID - to avoid confusion between networks, or to simplify your network advertisement. But, security isn't one of them, the AP is still beaconing, clients probe more (so you're wasting airtime and announcing the SSID anyways), and the SSID is sent in plaintext in association requests anyway, so it's not that difficult to find them.

But, there's yet another reason to avoid hidden SSIDs - especially if you want to take advantage of DFS (Dynamic Frequency Selection) in your WLAN:

I'll admit to doing "little contemplation" on this. Fortunately, I don't run into hidden networks that much these days (thank goodness), but I've also spent little time considering the consequences of DFS and hidden networks. Using hidden networks on DFS channels can cause unforeseen connectivity issues.

Clients can't actively probe on DFS channels. Active Probing is when a client send a "Probe Request". Clients  send probes on a channel to discover any potential APs. Since ACTIVE probing is not allowed on DFS channels, clients will do Passive Probes - which simply means they listen for beacons on a channel. Well, if they just happen to listen BETWEEN beacons, they’ll miss what they don’t see.

This also has implications for voice and roaming. If the clients can't probe for new APs then roaming times will be longer, and real-time data starts having issues. Many hospital deployments don't use DFS because of these issues.

Just food for thought. If you need frequency re-use (and these days who doesn't?) you'll need DFS. And DFS does not play well with hidden SSIDs. So, just stop hiding your SSIDs. Another thing you can do is mix your channel plan up so you don't have all DFS in an area. Always have non-DFS channel options available in case the device doesn’t have enough time to find the channel, or it doesn’t support it.

One final note, if roaming is important, you should be using 802.11r and devices that support it. And in conjunction with 11r use 11k/v to help speed up channel discovery. Of course, make sure your infrastructure and your devices support these features, and test them thoroughly to insure there are no compatibly issues when enabling them.

 

UPDATE: See the comment below by Andrew Von Nagy. It clarification  hidden SSIDs and DFS.

 

Actually, that isn't correct. Clients can't initiate transmissions on DFS channels, which prohibits most of the benefits of probing... namely faster discovery of the APs operating on the channel. But hidden SSIDs have no impact on this. Once a client hears a beacon on the channel by a "master" device (that must conform to radar scanning regulations) then it is safe for a client to probe.

So the real issue is two fold with DFS and client scanning:

1) Longer initial AP discovery time due to waiting until it hears a beacon (102.4ms intervals) instead of probing immediately (discover within just one or a few ms), and

2) Longer scanning time when roaming, especially for latency sensitive applications such as voice.

Whether or not the beacon populates the SSID IE field is irrelevant.


Cheers,
Andrew

♻︎ Today’s Quality Linkage

What is Your Wireless Engineering Worth? About doing things right.

Clarifying Wi-Fi Terminology webinar from iBwave featuring CWNE Alan Blake (@papageordy).

Co-Channel Interference (CCI), in the real world discussion at WirelessGeek.net on CCI and when it matters.

802.11 MAC Series – Basics of MAC Architecture – Part 2 of 3 from CWNP

802.11ax Proposed Enhancements for those interested in what's ahead.

Radio Frequency For Wi-Fi Administrators a Udemy course by GT Hill

Gravitational waves exist: the inside story of how scientists finally found them I love science!

Gravitational Waves Comic and Animation Even I can understand this!

This iOS date trick will brick any device [Video] Imagine someone spoofing an NTP server. 😱

The science behind OK Go’s latest jaw-dropping video Yeah, ♥ these guys!

SCIENCE! Gravity Waves are real. Guess that Einstein kid was right after all.

 from New Scientist:

Since gravitational waves were predicted by general relativity, they offer a chance to verify that Einstein’s theory really is the correct account of gravity. So far, general relativity is passing with flying colours: the observed signal is perfectly explained by Einstein’s equations.
But the real excitement is that gravitational waves can show us a side of the night sky we’ve never seen before. Until now, there had been no sign of black holes in this size range – much less two of them.

 

Science is cool. 

and from Scientific American: 

The discovery is not just proof of gravitational waves, but the strongest confirmation yet for the existence of black holes. “We think black holes exist out there. We have very strong evidence they do but we don’t have direct evidence,” Lehner says. “Everything is indirect. Given that black holes themselves cannot give any signal other than gravitational waves, this is the most direct way to prove that a black hole exists.”

 

Yeah, nerds, Black Holes are real! (Probably)

 

♻︎ Today’s Quality Linkage