Sniff Wi-Fi

A year ago yours truly wrote about the importance of device location when capturing Wi-Fi frames in a post titled, " Worthless Capture ".  Well, recently another Wi-Fi sniffing bugaboo has become more prevalent: devices that lack the physical capability to capture a  data frames. This whole problem really stems from 802.11n.  As many people (including the author) found out when the iPad was released in 2010, not all 802.11n devices have the same capabilities .  That is an annoyance to consumers, but it's downright dangerous to Wi-Fi professionals.  Most Wi-Fi networks require sniffing at some point (for surveying, for event preparation, for troubleshooting, etc.), but most Wi-Fi sniffing devices are incapable of sniffing high rate data frames. One more time: Most Wi-Fi sniffing devices are incapable of sniffing high rate data frames. The Linksys WUSB600N, which yours truly uses to sniff with WildPackets OmniPeek?   Only 2 radio chains (a radio chain ...

Ahh, mobility.  The bane of my (and many others') wireless humanity.  Wherefore art thou be so fickle?  Different devices roam differently.  Different apps make the same device roam differently.  And sometimes it seems that the same device and same app will roam differently depending on the situation.  So what can we do about it?  And, perhaps more importantly, how can a WiFi sniffer help? Let's face it, folks: nomadic WiFi is easy (comparatively).  At a university, you have students that want WiFi for their iPads in dorms, classrooms, labs, the basketball arena and at lunch.  But rarely in between.  A student using an iPad nomadically is just plain easier to support than a doctor who wants to pull up an X-Ray while she's moving or a retail manager that needs to see a picture from the Band of Outsiders fall collection while she walks over from the jewelry section. Compounding the mobility problem is that the iPad may not be your...

Sometimes I dream That he is me You've got to see that's how I dream to be The dream I riff, the dream I sniff Like Nate I want to be like Nate (Silver) Much has been made of the increased emphasis on statistical analysis, especially in the wake of New York Times blogger Nate Silver correctly predicting the electoral results for all 50 states in the recent United States presidential election.  Can analytics be applied to WLANs?  Of course they can.  It's just a matter of sniffing the right stuff. There are a lot of bad WiFi networks out there. There.  I said it.  It's out there and I can't take it back.  I see a lot of Wi-Fi in my travels.  Almost all of it could be improved upon and much of it seems like it was installed by folks with little understanding of how 802.11 networks work. So, what do we do to fix it? We can have best practices.  We can finally ditch automatic RF controls.  (Please, people.  If you haven't h...

The hot topic in WiFi nowadays is high density (HD), and for good reason.  It seems you can't swing a dead cat anymore without hitting some place (concert hall, convention center, tourist trap) where there's an attempt to offload cell phone data onto a WiFi network.  The most interesting thing about HD WiFi to yours truly is that it's the same fundamentals we've always known about, just recycled. If you were one of the lucky (unlucky?) ones to work in WiFi during its more formative years, you may have been taught certain basic concepts about WiFi.  For the author, fond memories still remain of sitting an Enterprise WLAN Administration course way back in 2003 (taught by noted Massachusetts Yankees fan David Westcott ) as part of my preparation for the certified wireless network administrator ( CWNA ) exam. What did Mr. Westcott teach us lo these many years ago? Plan out your space alternating between channels 1, 6 and 11 in the 2.4 GHz band. If APs are spaced t...

Yay, a new iPhone!   So sayeth me, my relatives (one of whom will receive my old iPhone), California (who will receive 8.75% in sales tax on the FULL UNLOCKED PRICE of the phone because California has a ludicrous sales tax law that taxes the pre-discount price of mobile phones) and anyone else who has been waiting for the iPhone to finally support 5 GHz WiFi.   But wait, there's more.  The iPad has long supported 5 GHz 802.11n WiFi, but the iPhone 5 does the iPad one better.  How?  Read on, amigos. Though Apple's most popular iOS device, the iPhone, has eschewed 5 GHz WiFi until iPhone 5, iOS-based access to 5 GHz channels (numbered 36 through 165) has been available in every iPad model. The iPad has always been 802.11n, which is good.  But the WiFi adapter in the iPad has always supported the bare minimum 802.11n , which is bad.  (Specifically, 65 Mbps Data Rate bad.)  This meant that an iPad is going to take about three times as much cha...

WildPackets OmniPeek has long been my favorite WiFi sniffing software, but lately this blog has been short on posts about it.  That needs to change.  So today I start a multi-part series (number of parts to be determined) on how I use OmniPeek to help me plan for and troubleshoot mobile devices. Mobility (defined here as seamless roaming between WiFi access points [APs]) is a longstanding enterprise WLAN issue that has kind of taken a back seat to supporting personal devices (a.k.a. BYOD).  For many enterprises, mobility remains important.  Car dealerships with push-to-talk handsets, warehouses with barcode/RFID scanners and retail locations with point-of-sale terminals are all examples of locations that require user devices to move around a large area without dropping connections, losing speed or experiencing choppy service. The solution to supporting mobility is to make sure that APs have adequate overlapping coverage without interfering.  It sounds simpl...

Oh, those darned iPhones. Can't live with 'em, can't keep your job without 'em. The vagaries of iPhones and other station devices are the most difficult part of managing a WiFi network, but there are some things that can be done on the infrastructure to try to make your stations work better. One of those things is lowering your AP transmit power to a level that more closely matches your client station's transmit power.  My main man G.T. Hill (of Ruckus Wireless ) recently wrote a blog post discussing why this post is bullshit. Now I'm going to tell you why his blog post is bullshit. (sorry, G.T.) G.T.'s primary point is that is is borderline mentally handicapped (politically correct term) to turn your AP's power down. His theory is that even if your client stations transmit at low power levels, having a high AP power level at least allows the from-AP data rates to stay as high as possible. (G.T. goes on to add that most traffic is downstream, th...