Sniff Wi-Fi

In the beginning, there was Coverage.  And so it was that 802.11 and his only begotten Son, WiFi were blessed upon PCMCIA cards who doth receiveth adequateth Coverage. And then as Coverage grew and the lands of Tablets wereth discovered, so came Capacity.  And thus did Capacity grow to represent all that was good and great about deploymenteths upon this fruitful land. And now, my Sons and Daughters, things have changeth again.   For Coverage and Capacity will both leave the Higheth of Densiteth WiFi wanting.  And so we shun them both.  For it is Neither -- Coverage nor Capacity -- that will taketh thy to the WiFi promised land. In case it was unclear, designing wireless LANs for Capacity has become an article of faith in some circles.  Keep it to 40 devices per AP.  Or 50.  Or 150.  Whatever the number is, the whole concept is misguided. WiFi uses radio frequency as its physical layer, and ther...

I've seen a lot of inexplicable stuff in my day.  Landlords advertising Free WiFi and then telling you to use the neighbor's.  Twitter praise from people whose employer I had just criticized in a blog post.  USC journeyman quarterback Mark Sanchez picked fifth in the entire NFL Draft.  But when I saw that my sturdy Apple Airport Extreme (single radio, dual band, two-stream 802.11n) wireless router was tagging all of my apps as Background traffic, I just couldn't explain it. For those who are unfamiliar with WiFi quality of service (QoS), a quick primer: WiFi Multimedia (WMM) certified devices use QoS protocols from the 802.11e amendment.  Primarily, that means classifying APPLICATIONS (not networks, not devices) as either Voice, Video, Best Effort or Background.  What happens when a device classifies an application as Voice (highest priority)?  Whenever that device is ready to send a frame (sometimes called a packet) from that ...

I recently got into a little tiff on Twitter.  In part it was an argument about blogging and reaching a broad audience, but mostly it was about site surveys.  Site surveys are hot right now, but I find that surveyors often overlook an important aspect of WiFi: different devices act differently. Conventional wisdom for WiFi site surveys is to get some site survey software , upload a floorplan and start a-surveyin'.  First predictive (letting the software estimate where coverage will go), then active (temporarily mounting access points in the locations chosen in the predictive survey and testing connectivity) and finally verification (walking the site after APs have been installed). The problem with all three types of surveys (predictive, active and verification) is that they are done with site survey software.  Site survey software is great for selling APs or pacifying execs, but it usually requires using a specific adapter.  So every time you verify conn...

I defend Apple a lot.  When Network World wrongly accused  the original iPhone of flooding Duke University's network, I defended Apple .  (It was later found to be a Cisco problem.)  When a health care provider I was doing some work for blamed SIP-enabled iPhones for a VoIP problem, I eventually found out that the APs were to blame .  (The APs were failing to respond to WiFi frames tagged as "Background" QoS.)  Time and time again networking folks blame device makers like Apple, and time and time again the problem ends up being the network. There are times, however, when it really is Apple's fault.  When the network is operating just fine.  This is one of those times.  The problem is that I just don't know why. 802.11n (HT) and 802.11ac (VHT) networks operate in co-existence with first generation (802.11a/b/g, that is) WiFi a lot.  When that happens, the HT or VHT access point o...

Yours Truly has been worried about the future of WiFi sniffing.  Yours Truly worries about the people (they seem to prefer site surveyors) the software (AirMagnet has yet to support 802.11ac adapters) and the methods (WildPackets has been pushing AP-based capture).  To a person who believes that portable WiFi sniffing is essential for optimizing WiFi performance, it is all very disconcerting.   And yet, there is hope.  WiFi sniffing is ready to step into the 802.11ac/Internet of Everything era, and here is how it can be done. WildPackets OmniPeek has long been the author's favorite WiFi sniffer, but it only runs on Windows.  For years and years and years that was fine.  There were always a few Windows-compatible WiFi adapters that worked great with OmniPeek.  Now, however, WildPackets has gone in a different direction.  They are promoting WiFi sniffing via an AP (which often results in a wor...

So I'm milling around Twitter one afternoon when someone told me that Fluke AirMagnet WiFi Analyzer was overwhelming.  Well, it is if you don't know what to look for.  And since I'm in the midst of developing an online class about WiFi sniffing, I decided to whip up a shabby-looking 10 minute video that might help those who feel overwhelmed. If you like my blog, you can support it by shopping through my  Amazon  link or donating Bitcoin to  1N8m1o9phSkFXpa9VUrMVHx4LJWfratseU Thank you.

When I wrote a blog post recently extolling the virtues of WiFi protocol analysis, I expected some blowback.  Not because WiFi protocol analysis won't help performance (only a Garo falo -ian fool would assert that it won't), but because I touted protocol analysis at the expense of spectrum analysis.   Well, it's time to make amends.  Spectrum analysis is pretty darned useful, too.  And the spectrum analyzer that I use ( Metageek's WiSpy DBx with Chanalyzer ) underwent a notable update in recent months.  Here, then, is an update on Chanalyzer and a reminder of what spectrum analyzers can be useful for. For quite some time Metageek's spectrum analysis suite (consisting of the WiSpy USB adapter and the Chanalyzer software application) has been the thrifty man(and woman)'s tool of choice for analyzing WiFi frequencies.  The original Metageek WiSpy (a 2.4 GHz-only device without an external antenna interface) was a $100 (all prices in USD) USB adapter and ...