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Eighteen Seconds of (a Very Chatty) iPhone

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The iPhone 5 is a chatty device.  How chatty?  I checked, and it is chattier than I thought.

Yours truly has done more WiFi sniffing of iPhones than yours truly cares to recount.  What has always stood out about these captures is the amount of chatter than an iPhone seems to engage in.

I did a little test of my unlocked iPhone 5 to see exactly how chatty it was.  The test involved me turning on the phone’s screen, spending a second looking at iMessage (which happened to be the last app I was on when the screen was turned off), pressing the Home button, opening the Twitter app (because, after all, if you’re not on Twitter these days then you’re not wasting your time properly) and refreshing my Twitter feed.

The test took about fifteen seconds.  My capture saw WiFi frames going to or from my phone for about 17.64 seconds (rounded up to 18 for the purposes of a catchier blog post title).  Here is what it looked like:

The good news is that my phone was using high rates for data.  The highlighted frame above traveled through the air at 121.5 Mbps.  Some of the data frames even went all the way to the iPhone 5’s maximum data rate, which is 150 Mbps.  (And pay no attention to the 6 Mbps or 24 Mbps frames.  That’s control traffic.  Nothing you can do to escape that.)

The bad news is that my phone was very active on the channel despite the fact that all I really did was turn the thing on and refresh my Twitter feed.  Check out the stats from my capture:

The “Displayed” statistics are representing my phone’s traffic only.  And what happened in that 17.6 seconds?  268 kB (or, 0.268 MB if you want to look at it that way) was send across the wireless channel.  That is a pretty large amount of stuff for a simple Twitter feed refresh.  Imagine if I tried to look at a photo or browse the web.

So the iPhone is a chatty Cathy.  It’s not very chatty when the screen is off (unseen above is the fact that the first frame with my phone’s address was sent a full 10 seconds after I started capturing, which coincides with the time I turned on the phone’s screen), but once people start using their iPhones those babies get active even when the user isn’t very active.

What does all of this mean to us?  One thing it means is that conserving battery life ain’t just for the Sierra Club.  Users who keep their screens off are also keeping our WiFi networks clear.  The other big takeaway is that app developers don’t care about us.  They’re gonna make their apps the way they want to make their apps.  I’d bet dollars to donuts (a cliché that no longer makes sense, but still) that developers from Twitter and Apple could have made the iPhone 5 a lot less active on the WiFi channel if they’d have wanted to.  Typically it takes a crisis for app developers to reel in their network consumption.  Who knows if that will happen any time soon.

Written by sniffwifi

August 30, 2013 at 10:52 pm

Posted in iPhone 5, WiFi traffic