Sniff Wi-Fi

Wi-Fi Calling is here, and that fact is causing concern for some Wi-Fi folks.  Wireless LANs that were initially installed as a value-add may be tasked with carrying mobile, high-quality, always-on voice traffic. The 802.11 standard has had quality of service (QoS) protocols designed to accommodate voice since 2005, when the 802.11e amendment was approved.  That's good.   What's bad is that some voice applications are over-prioritizing their voice traffic, and it could lead to capacity limitations. First, some background on Wi-Fi QoS: The original 802.11 standard deigned that all Wi-Fi traffic would be created equally.  That is a GREAT thing for most Wi-Fi networks.  If some namby-pamby user whines to an admin, "Hey, why are you placing that AP in the OTHER room?  I want the AP closer to me," the admin can tell him (or her; women occasionally complain, too) "look, buck-o (or, buck-ess), Wi-Fi gives equal throughput to everyone who's connected.  ...

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 ...

Auto-channel selection protocols have been an increasingly common source of controversy for enterprise Wi-Fi administrators.  Aruba's ARM, Cisco's RRM, Ruckus's ChannelFly and Aerohive's ACSP all allow a centralize management entity -- either controller or software -- to automatically set the channels of access points (APs).  These protocols can be big time savers during the surveying and implementation stages, but also can cause big headaches once the Wi-Fi is up and running.   The argument over whether to use auto-channel selection protocols may be coming to an end, however.  802.11k is becoming more widely supported in Wi-Fi devices, and when smartphones, tablets and other devices support 802.11k, the decision is a no-brainer: auto-channel should be avoided because it makes roaming worse. To understand the impact that 802.11k (radio resource measurement) has on Wi-Fi devices, one first must understand a fundamental fact about Wi-Fi: devices control connectio...

Apparently Wi-Fi at the White House sucks !  A journalist asked me what might help it, so I figure I'll share my response: Hi [Very Wise Journalist Who Reached Out To Me, Ben Miller, For Comment], In some ways the White House is like any other large, multi-user space and in other ways it is very different. Uncommon challenges at the White House are likely the result of security requirements and the need to maintain the historical integrity of the building.  The White House almost certainly has areas that are off-limits to AP installers and there may be limits on where cable drops can be made. There is a distinct line between good and bad solutions when AP locations are restricted.  The goal of both solutions is to increase coverage to hard-to-reach areas.  The bad solution, which is likely happening at the White House, is to increase the transmit power of APs.  Increasing AP transmit power aids downlink data sent from an AP to a Wi-Fi device, but ...

Everybody likes high Wi-Fi speeds.  Because high Wi-Fi speeds mean that the channel is being used more efficiently ( often false ).  An efficient channel means that there's more available throughput ( only in sterile test environments ) and more available throughput means that more users can be supported concurrently ( completely wrong ). Unfortuantely, high Wi-Fi speeds sometimes  ( all the time )  come at a cost.  To get higher Wi-Fi speeds, wider channels must be used ( which makes the Wi-Fi suck ).  Using wider channels means that fewer channels will be available ( plus it ups minimum RSSI requirements, which just about guarantees a bad design ).  It is therefore essential that wireless professionals analyze the environment and carefully choose whether to use 40 MHz or 80 MHz wide channels ( or they could stop wasting everyone's time and just stick to 20 MHz channels ). But this blog post isn't about choosing the correct channel bandwidth...

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 rec...

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 relati...