Sniff Wi-Fi

I have some interesting stuff about the topic that this blog is supposed to be about (WiFi sniffing) coming soon.  I promise.  But the FCC made some news concerning WiFi today, and I want to help people understand it. This post is happening because of what the FCC did in March, 2014.  What the FCC actually did was (probably) kill WiFi channels 52 to 144 by imposing new rules (the effects of which we have yet to see, because APs approved by the FCC prior to March, 2014 do not have to follow the new rules) that make WiFi devices more likely to work poorly when Doppler RADAR is on those channels.  What the FCC claimed they did was " increase availability of spectrum for high speed, high capacity " WiFi. Technically, the FCC can claim to be something other than liars.  The March, 2014 rules did increase spectrum availability in a narrow sample of use cases.  What was really going on, however, was the FCC doing the bidding of Doppler RADAR operators (who, ...

If there's one thing we've learned about WiFi over the years, it's that problems get fixed.  Site surveys used to be sooo annoying.  So we got controllers with auto-RF.  Guests used to complain and complain that we didn't have WiFi for them.  So we got captive portals.  And so the worl-- Wait a minute.  Auto-RF really doesn't work and we still need site surveys.  And captive portals annoy our friends in desktop support as much as they annoy our guests, plus they drag down overall WiFi performance.  Hmmm...  Let's start over: If there's one thing that we've learned about WiFi over the years, it's that sometimes what seems like a good solution to a problem only ends up making things worse.   Which brings us to our latest solution-that-only-makes-things-worse: Dual-radio APs with band-selectable radios. A little background: Last week, I was sitting in an office, minding my own business when I got a call.  A friend of mine wh...

Voice over WiFi is scary.  Retries, packet errors (due to lots of Retries) and high latency (usually due to packet errors that happen because of lots of Retries) will murder a WiFi network's ability to handle Voice and leave your users screaming (not actually screaming) like they were cast in a horror movie (or, at the very least annoyed like a character from Office Space).  But there's one thing that sometimes scares people, but really shouldn't: Voice Arbitration.  It's not going to kill your WiFi voice calls.  In fact, it will almost certainly help. Arbitration is a process defined in the 802.11 standard .  Every device (client/station and AP) goes through it. The simplest way I can describe 802.11 Arbitration is like so: If your AP or station has heard a quiet channel for 37 microseconds (0.000037 seconds), then your AP or station transmits a frame (what most people call a packet, but I call a frame). If your AP or station has been hearing a busy ch...

Nine months ago (bad way to start a blog post, I know) I wrote a blog about the future of WiFi sniffing .  In the comments section (perhaps the only worse thing for a blogger to say), someone mentioned a free, Windows-based application called Acrylic WiFi .   I briefly checked out the app and dismissed it as yet another Discovery utility disguised as a something more.  Then I actually used Acrylic WiFi and...  it works!  It sniffs WiFi frames (sort of) and it does it for free (outside of the cost of an ordinary 802.11 USB adapter)!  This changes everything (kind of)! For years, the method for free WiFi sniffing on a Mac has been simple.   Head down to the bottom of this post for a reminder. Now, we can do similar things in Windows.  It's not quite as simple and it's not totally free, but it works (pretty much). 1. Download and install  Acrylic WiFi Free , including Monitor Mode support (and, actually, if you can find an ol...

802.11ac is the latest and greatest WiFi standard, but it's confusing.  So many questions: Is it really that much faster than 802.11n? (It can be.)  Is it worth upgrading?  (Probably not in the enterprise, but at home, absolutely.)  How fast is my device?  (Data rates as low as 6.5 Mbps and a high as 1.3 Gbps.)   Getting specific answers to 802.11ac performance questions can be a chore sometimes, but there's a simple way to check your APs.  All you need is a wireless sniffer and about five minutes. Today I wanted to find out what my 802.11ac AP is capable of.  I suppose I could've gone in search of a data sheet, but instead I decided to break out the wireless sniffer.  It was a quick and simple process. Step 1: Find the channel of your AP If you're a Mac OS X user, you can use Wireless Diagnostics .  If you use Windows, then Acrylic WiFi is probably your best option. My channel was 48. Step 2: Capture on your channel  ...

Spec-ing the Layers with WiSpy (one time, one time) Channel gone red with this stream (two times, two times) Killing my channel with this song Killing my WiFi With this song Taking my WiFi With this stream Killing my WiFi With Bluetooth spe-ee-ee-eeakers... Wireless streaming (music, video or, in the case of the wonderful song referenced above, a music video ) can sure kill a WiFi connection.  It's good to have a spectrum analyzer to identify the problem.  It's even better to remember to use it. Wireless streaming devices are popular nowadays, but most of them are benign.  An AppleTV, for instance, can wirelessly stream audio and video or it can act as a mirroring device for whatever audio or video is on your smartphone, tablet or laptop.  (And mirroring is tougher on WiFi than basic streaming.  When I mirror my iPhone 5, I'm creating three streams.  One from my wireless router to my phone for the Internet stream, a second from my phone back ...

Chatty smartphones have been an issue for years.  Whether you're concerned with security or performance  (or both), the amount of Probing being done by unconnected iPhones, Galaxies and the like has been worrisome.   Today, things have changed.  Smartphones don't Probe as much.  This is probably for the better, but there could be a catch. I'm an Apple guy.  Even when I was using PCs in college (things were different back in the 90's , I tell ya), it was always because they were free.  Once I finally had to buy a computer, I went straight to the very first iBook in 2001.  I own an iPod, iPad, iPhone and MacBook Air.  My next computing purchase will probably be an iMac (to better record those promised-but-not-yet-delivered online training videos on WiFi that I touted six months ago).  So, I like the company.  And I like bashing its competitors sometimes.  (Not my most magnanimous trait, but nobody's perfect.) I liked poi...