Sniff Wi-Fi

  Show  of hands: Who here has seen Retry percentages above 90%? If you work with Wi-Fi, your arm is likely reaching skyward as if you're hiding Darrell Lea licorice from the kids. (Hope you wore deodorant today.) Juniper Mist is most notorious for it. Nyansa Voyance -- which is no longer a Wi-Fi thing -- used to do it too. Aruba Central even has a built-in alert for it. The problem is, 90% retries doesn't really exist (and of course, 100+% retries is impossible). When an AP repeatedly sends retransmitted frames (packets) to a Wi-Fi client -- and let's pause to point out that centralized WLAN management systems can only reliably know AP-to-client (not client-to-AP) retry statistics -- the AP will typically drop a packet before re-sending it so  many times that the wireless retry percentage would ever truly hit 90%. So why, then, do we see retry percentage near, at or above 90%? Because some (most?) Retry% calculations often use a denominator of successful  frames in...

Last week's blog about Wasted Wi-Fi prompted some questions about AP transmit power in the enterprise.   Let's answer some of those questions by doing a little Q(-Tip)&(802.11)A, an exercise in which we watch a Q-Tip video before Answering a few questions about Wi-Fi. You've seen the Q(-Tip), now on to the A(nswer)s: Wasted Wi-Fi is all about APs and/or stations making inefficient use of a Wi-Fi channel.  When Wasted Wi-Fi happens, either data rates are lower than they should be, or Retry percentages are higher than they should be. The Q becomes, where do equivalent isotropically radiated power (EIRP), transmit power and conducted power fit in? The A is, higher data rates and lower Retry percentages tend to happen when signal-to-noise ratio (SNR) is higher, and higher EIRP/conducted power/transmit power leads to higher SNR. In other words, if you talk louder, then people hear louder.  When people hear louder, they have a better chance of being...