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An Android Change for the Better (Maybe)

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Chatty smartphones have been an issue for years.  Whether you’re concerned with security or performance (or both), the amount of Probing being done by unconnected iPhones, Galaxies and the like has been worrisome.  

Today, things have changed.  Smartphones don’t Probe as much.  This is probably for the better, but there could be a catch.

I’m an Apple guy.  Even when I was using PCs in college (things were different back in the 90’s, I tell ya), it was always because they were free.  Once I finally had to buy a computer, I went straight to the very first iBook in 2001.  I own an iPod, iPad, iPhone and MacBook Air.  My next computing purchase will probably be an iMac (to better record those promised-but-not-yet-delivered online training videos on WiFi that I touted six months ago).  So, I like the company.  And I like bashing its competitors sometimes.  (Not my most magnanimous trait, but nobody’s perfect.)

I liked pointing out that Google’s Android operating system had worst wireless security than Apple’s iOS.  Including:

-Apple requires server certificate validation by default for WPA2 Enterprise authentications (even if it is user-controlled), while Android does not.

-Apple smartphones and tablets Probe only for hidden SSIDs, like so:

(That’s a Probe Request filter in WildPackets OmniPeek.  The SSIDs that you see in those Probe Requests are all hidden SSIDs, with the exception of “Google Starbucks”.  Read on to learn why my local Starbucks’ SSID is showing up in there.)

-Android smartphones and tablets Probe for all saved SSIDs.

At least, they used to.

I was demonstrating the inferiority of Android’s wireless security recently when I learned something new.  They’re not inferior anymore.  Some time recently (or, at least in between the time of my previous Android OS update and my recent update to Android 4.2.2) Google changed Android devices’ wireless behavior to match that of Apple’s.  Android smartphones and tablets started Probing for hidden SSIDs and staying quiet for broadcasting SSIDs, like so:

Of course, I was ambivalent.  GOOD that Android devices’ wireless security has improved!  BAD that I can no longer tout Apple devices’ wireless security superiority in comparison!

So, there you go.  A begrudging admission that Android’s wireless security has been shorn up to match the level of Apple’s.  (In fact, Android’s wireless security is even considered superior in some circles because Android has an option to eliminate user-based verification of server certificates during WPA2 Enterprise authentication.  But we don’t need to discuss that right now.)

But… (and, there’s always a But)

…this may actually be bad for mobility.

Apple iOS and Android devices don’t Probe unless they connect to a hidden SSID.  Nice.  But, let’s take a step back.  Why is Probing in the IEEE 802.11 standard to begin with?

Probing (a process where a client/station device sends a Probe Request frame in order to elicit a Probe Response frame from an access point [AP]) is in the 802.11 standard to facilitate mobility.  Roaming.  Handoff.  Whatever you want to call it when someone moves out of the range of one AP and into the range of another.  Probing also helps devices connect more quickly when starting/waking up and can help devices find an AP in areas that are congested with neighboring WiFi devices and APs.

So, Probing can be a good thing.  Especially for mobile devices in crowded areas.  And now Android devices (like Apple iOS devices) do less of it.

If you say to yourself, “gosh, this iPhone/iPad/Galaxy/HTC One seems to really crap out when I go to a crowded place” (like the Starbucks by my place in Los Angeles), then you might want to ADD Probing to your device.  How?  By tricking your device into thinking that the SSID is hidden.

That’s what I did at my local Starbucks.  My phone sends out these Probe Requests…

…because I manually added the “Google Starbucks” SSID to my phone.  Instead of tapping on “Google Starbucks”, I tapped Settings -> Wi-Fi -> Other… (ellipse in the GUI, not added by me) once I got in line for a Tall Skinny Peppermint Mocha, Hold The Whipped Cream and then typed in “Google Starbucks”.  I don’t know if it helps a whole heck of a lot (Starbucks still uses the darned Captive Portal, which will slow down any wireless connection), but it does optimize a couple of things.
In summary, Android’s move to Apple-like wireless behavior is good for security and overall channel performance.  But if your problems are mobility and speed of connectivity, then you might want to un-do what Android has done by adding your SSID manually.
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Written by sniffwifi

December 19, 2014 at 8:33 pm

iPhone 5 Probes the Right Way, Too

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Quiet when standing still; active when moving.  That is the way that WiFi devices should treat Probe Requests.  Android devices (at least, Android devices that act like yours truly’s Samsung Galaxy Tab 2) probe the right way.  After doing a quick test on the iPhone 5, it appears that Apple has their devices probe based on movement as well.

Apple iOS devices have a terrible reputation in some WiFi circles.  The author has heard complaints about mobility, stickiness, throughput capabilities and just about anything else under the sun.  Heck, just today an article was published decrying the throughput (WHO CARES?) limitations of of the new MacBook Air (not iOS, but still Apple) was viral’d around the web.

To check to see if the iPhone 5 matches the probing behavior of an Andoid device, I associated the iPhone to the office network on channel 36/+1 and started a capture on channel 44/+1.  Then I got up from my chair and started walking around while continuing to use the iPhone.

The results were this:

Notice that the Probe Request frames started coming out immediately when my phone began moving, but then stopped less than one second later.  Most likely what happened was that when I got up from the desk, the iPhone sensed movement and began probing for the next highest 40 MHz channel.  Then the phone probably went from channel to channel as it continued to probe.  All the while the phone continued to stay on channel 36/+1 as much as possible in order to keep communication with the network.
Of course it is hard to draw firm conclusions from a few minutes worth of Wireshark captures, but to these eyes it appears that Apple may be taking steps to get iOS devices in the good graces of WiFi admins and other professionals.  

Written by sniffwifi

June 24, 2013 at 11:13 pm

That Android is Quite the Prober

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No bold type introducing today’s post, as I’m going to keep things short.

I was doing some work last week looking at Android devices (specifically, a Samsung Galaxy Tab 2) and I noticed some very heavy probing behavior.  We were checking out the device’s behavior when it moves from AP to AP, so I set a capture for the target second AP.  I did the test (things went fine, but the WiFi Analyzer app in particular seems to really make Android devices stick to their currently associated BSS) and looked at the capture.

Seeing a ton of Probe Requests from the Tablet was expected.  What wasn’t expected was the Android tablet probing even while associated to the first AP.  Even when the received signal was strong (in the -50 to -63 dBm range), the Android was going off channel to probe and probe excessively.

At this point I’m still trying to figure out if physical motion or an app (or lack thereof) caused the probing.  One thing I am pretty confident in saying already is that updates to Android OS and iOS (the one for iPads and iPhones, not the Cisco one) have really seen the two leaders in mobile operating systems take divergent paths concerning WiFi overhead.  Apple seems to be making their smartphones and tablets probe less, while Android devices are probing just as much, maybe even a little more.

Written by sniffwifi

June 3, 2013 at 10:36 pm