We all do it. We know we do it. And we think nothing of it. We bring our mobile devices with us wherever we go, including the office. But we don’t use them most of the time. They just sit there disconnected from the wireless LAN, waiting for us to use them on the cellular network. 問題ありません。But then again, there could be.
What some people may not realize is that these devices are constantly transmitting probes for Wi-Fi networks that they have previously connected to, or for which they have been configured. This includes corporate networks, the users’ home networks, and even hot spots from a hotel or the last conference attended.
Now, Wi-Fi villains know this well. Many honey pot attacks and similar plots exploit this to lure a “driverless” mobile device to connect to the villain’s own access point, allowing the villain to begin wreaking havoc with the unsuspecting victim.
But the problem is more than just this. These disconnected Wi-Fi devices actually impact the performance of Wi-Fi networks for connected devices. Enough of them can cause issues for the IT staff responsible for ensuring the corporate Wi-Fi network performs well for people accessing business-critical systems every day. You see, the probes transmitted by these devices, although short in frame length, are sent as excruciatingly slow speeds. These slow speeds require more airtime to transmit. This is the same airtime that is shared among connected devices that are used by people trying to get their work done. With enough disconnected devices transmitting enough probes, the result is a significant percentage of the shared airtime being effectively wasted.
Think of it as your family’s dinner table conversation where everyone has something to say, but a neighbor sitting right outside your open window keeps chiming in with nothing to say but says it slowly and frequently, constantly interrupting the conversation.
This does not mean that IT policy makers need to forbid BYOD. It simply means that for those responsible for the great (i.e., heavily used) Wi-Fi networks of the world, we need to determine how much of a problem this can be for a specific network, and ensure the issue is kept in check.
This new white paper by Wi-Fi expert Ben Miller describes how Wi-Fi-disconnected devices operate, even when connected to a cellular network. Using the AirMagnet WiFi Analyzer PRO, Ben shows in simple examples how to quickly determine the impact they can have on the precious resource of Wi-Fi airtime, as well as how to identify particularly chatty devices.