Sniff Wi-Fi

After eight and a half years, one hundred forty posts, and a shade under one-and-a-half million page views, it is clear to me that one topic causes more controversy than any other on this here Sniff Wi-Fi blog: disabling low OFDM rates (such as 6 & 9 Mbps). Wi-Fi vendors tell you to do it. CWNP trainers tell you to do it. Other bloggers tell you to do it. I (and a very, very small group of other hardcore Wi-Fi professionals) tell you   not to   do it . But this blog post isn't about re-litigating that controversial issue (for the most part).   This blog post is about telling you why I **did** disable the 6 & 9 Mbps data rates on a recent Wi-Fi optimization project. Given the subject matter of this blog post, I feel compelled to begin with some shameless self-promotion: if you have a problematic Wi-Fi deployment (or if you're in the "design" phase and you want to avoid having a problematic Wi-Fi deployment, or if you would like training on how to a

Recommending the exact opposite of what every enterprise Wi-Fi infrastructure vendor recommends can be awkward.  As awkward as the first meeting between Hank Kingsley (Jeffrey Tambor) and the Wu-Tang Clan?  (WARNING: extremely NSFW) Maybe not that awkward.   But while Hank had trouble relating to Wu-Tang member Ghostface Killah, Wi-Fi folks can avoid trouble by being aware of an increasingly common problem, the Ghost Frame Killah. Ghosts, as we all are well aware, are apparitions that can have a detrimental effect on buildings built on Indian burial grounds, while remaining unseen to our earthly eyes.  If you have Ghosts, you may need to call a Ghost Bouncer to solve the problem. Ghost Frames, on the other hand, are Wi-Fi frames ("packets") that can have a detrimental effect on Wi-Fi networks, while remaining unseen to our earthly Wi-Fi sniffing tools.  The solution to Ghost Frames is a simple one, but one that requires Wi-Fi folks to do the exact opposi

The last Sniff Wi-Fi post; on why Wi-Fi professionals should stop disabling low data rates, was met some resistance.  Be it in the comments  or  on Twitter , several experienced Wi-Fi folks disagreed. All arguments in favor of disabling low rates  (the ones that were presented to me, at least) were refuted in the text of the Leave, Leave, Leave My Rates Alone blog post.  But text is a less accessible messaging method.  "A picture is worth a thousand words", as the old saying goes. If pictures will get the message across better, then pictures are what I'll use.  What follows is an illustrated look at why disabling low data rates is a bad idea. It's gauche to begin an illustrated work with text, but to understand the problem with disabling low Wi-Fi data rates one must first accept some facts about Wi-Fi devices (smartphones, laptops, etc.): 1. Wi-Fi devices -- not APs -- control associations and roaming. 2. Wi-Fi devices roam based on low received signal str

Sometimes you have to return to the classics.  Who better than less-than-memorable pre-gangsta rapper Hi-C to take us there? Much like the cool kids have embraced the neon colors and late-night TV comedy of the grunge decade, so too has this blog decided to embrace its past, only with a twist.  Five short years ago I  wrote a plea asking that Wi-Fi folks stop disabling high data rates on guest networks.  And they did!  (For the most part.)  Unfortunately, the pendulum has swung too far.  Now it's time to ask Wi-Fi folks to stop disabling low data rates; or, to paraphrase Hi-C: leave my rates alone. Wi-Fi folks are always looking for ways to make wireless channels more efficient.  That is a good thing.  Wi-Fi's one limited resource is channel time, and so it is great to see more and more Wi-Fi people looking for ways to get the most amount of data across a channel in the least amount of time. Disabling low data rates is a relatively recent trend that aims to impro

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  Using a professional protocol analyz

As long time readers of this blog might know, WildPackets OmniPeek has been my favorite WiFi sniffer for nearly a decade.  Then I found out about WildPackets' OmniWiFi 3-stream 802.11n USB adapter and I fell even more in love.  Now I learn that OmniPeek 7.5 has added wireless features to the Compass screen.  A good product has been made better (though time will tell if it lasts). First, OmniWiFi: The fact that different 802.11n devices have different capabilities is one of those things that sometimes flies under the radar.  The standard may say 600 Mbps, but just on the Apple website one can buy 802.11n devices with maximum rates of 65 Mbps (iPhone 4S), 150 Mbps (iPad Mini), 300 Mbps (Macbook Air 2012) and 450 Mbps (Macbook Pro 2012). 450 Mbps WiFi devices are the ones that give WiFi pros trouble because so many sniffing tools fail to capture 450 Mbps traffic.  The popular (at least with Wireshark devotees) AirPcap NX from Riverbed, the beloved (at least by yours truly) D-Lin