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Go To Sleep, Go To Sleep, Go To Sleep Little iPhone

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In some circles, Apple Wi-Fi devices are knows to have problems with lost connections.  iPhones and iPads will unexpectedly miss incoming calls, have delays in receiving push notifications and even be forced to reauthenticate. There is a solution to Apple devices' connection problems, and as with most "device problems", the fix resides on the infrastructure.  The DTIM setting needs to be increased.  ( Apple recommends a setting of 3 or higher .)  Here's why: Some Apple Wi-Fi connection problems stem from Apple iOS devices' use of 802.11 power management.  To understand what Apple devices are doing with power management, one must first understand how 802.11 power management works. Let's start with unicast data.  The 802.11 standard allows devices' Wi-Fi radios to enter the Doze state in order to conserve battery life.  Wi-Fi radios in the Doze state are unable to receive data from the AP, so APs buffer all unicast data that has a destination MAC addr
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Why Are You Slowing Down My WiFi, Apple? To Make Things Better?

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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 operates in mixed mode. There are all sorts of ramifications when a WiFi network
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Why You Should Stop Disabling Low Wi-Fi Rates, Illustrated

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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
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