
How a law firm tested "phantom" AT&T smartphone data use - shawndumas
http://arstechnica.com/apple/news/2011/05/lawsuit-alleges-att-overcharging-smartphone-users-for-data-use.ars
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dangero
Their testing methods were very imprecise.

To really confirm this they would need to monitor the network driver(s) on the
phone and record the exact data amounts that are passed and then compare that
to what AT&T reported.

Another option would be to emulate a cell tower, connect the device to it, and
monitor traffic that way.

The thing I did find interesting was that they said some carriers round up
transfer sizes. That could account for some big differences when you consider
that this rounding could happen per transfer or session. To me that sounds
like highway robbery akin to shaving pennies off interest.

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_-af-_
You can't easily 'emulate a cell tower'.

To verify that the device isn't indeed transferring any data as part of any
background Apple process they should put it on WiFi and monitor traffic
through the router. It should be zero.

I'm logically assuming that any background process that would transfer data
over 3G would also do it when on WiFi network.

They could also get a data modem from AT&T and test it by connecting to the
tower but not transferring any data. If AT&T is overestimating data transfers
or has phantom data then it would be across the board and would also show up
on transfers through their data modems not just their iPhone plans.

~~~
joshu
Actually, it is doable. I met a guy that had a whole SDR plus GSM stack. I was
able to pair my blackberry with it. He runs a cell network at Burning Man,
apparently.

~~~
bostonvaulter2
Was going to mention the system at Burning Man, then I realized that you
already mentioned. So here's the link:

[http://www.networkworld.com/news/2010/083010-open-source-
voi...](http://www.networkworld.com/news/2010/083010-open-source-voip-cell-
phones-at-burning-man.html)

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mentat
So AT&T relies on nightly checkins from the device reporting how much data it
uses? They don't do the accounting in the network? That seems _crazy_. So on a
jailbroken device you could just tell it to report 10% less and it would all
be even.

~~~
otterley
I don't think that's how it works. I think what the speaker meant is that the
accounting data is forwarded from the local access point to the billing system
at the end of the day.

~~~
mentat
From the article, "the time stamp reflects the time that your device
established a connection to the [billing system], not the time that you sent
or received data." Note the "your device".

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Bo102010
Clearly this guy's test was incomplete and guaranteed to give the result they
sought...

However, I have worked in capacity planning at a mobile telecom, and it's
scary how confused that alleged experts are about "bytes" and "bytes per
second."

Given that experience, I'm not surprised that AT&T would get "bytes
transferred" wrong, but I think it's more likely due to incompetence and not
malice. I wouldn't be surprised if they underbilled people also.

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jevinskie
Why didn't this researcher run tcpdump on all of the iPhone's network
interfaces or use sysctl to measure actual data usage?

~~~
mirkules
Presumably because he was connected to the 3G (or other data) network. Unless
he can run tcpdump on the iPhone itself or become a man in the middle between
the iPhone and the data network, he couldn't capture traffic.

An interesting test would be to connect the iPhone to a regular wireless
router, measure the activity, then compare that to billing activity. Although
my Android Galaxy S, for example, connects to the data network to look for
updates _even though it is connected to a wireless network_ \-- so this test
could be moot.

~~~
jevinskie
With a jailbroken iPhone or a Nokia N900, tcpdump works just fine.

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germancito
I've compared the network usage as reported on the iphone with the one AT&T
measures, and it's not the same. I've paid over-usage fees at times when
according to the iphone reading I had 20 MB left. Now it all makes sense...

~~~
sukuriant
Where did it say you had 20MB left? Were you using ATT's evaluation? Or a
third-part app? Or, the iPhone's operating system, itself.

If you're using the iPhone's operating system, ATT may be calculating space,
and rounding up in a different way from Apple. (Examples of this exist in
other child-comments of the OP)

