A recent article in the New York Times points the finger at iPhone users for slowing down AT&T’s cellular network.

The article charges that iPhone users use Internet connectivity more than other smart phone users, creating a wireless logjam of Tweets, Foursquare updates and Uno challenges.

That we use more bandwidth should seem obvious to most iPhone users; we chose this phone because it makes Internet connectivity so easy.

Maybe the accusers have a point. After all, it’s not as if the iPhone has a meter we can consult to see how much data we’re using at a given time. It’s not as if we have a natural, built-in sense for how much we are using, as we do for drinking water or eating food. Still the amount of data consumed by iPhone users is pretty substantial compared to a regular cell phone. In fact, compared to other smartphones, the iPhone is a downright data hog.

According to research by Chetan Sharma Consulting, the average "feature-filled" cell phone user consumes 40MB of data during a month. The average smartphone, 140MB over the same time period. T-Mobile's G1 with the Google Android OS sucks down around 300MB on average per month. The average iPhone data sucked down during that same month? A whooping 500MB.

That's just the average, there is a good chance that if you're the kind of person that partakes in all the social media out there and tries a few new apps a week, it's possible you're downloading more than that. 

So which of the most used apps are straining the network? Not every app needs gobs of data from a network.
 
We looked at 20 popular apps to get an idea of how much data each sends and receives in its first 30 seconds, and the in its first three minutes, to get a sense of whether the criticisms were on the right track.

Methodology

We installed Wireshark, a network tool that lets us peek at network traffic, on a 3.06 GHz Core 2 Duo iMac. This iMac connects via Ethernet to our Airport Extreme router, which connects by Ethernet to our cable modem. Then we turned on Internet sharing on the iMac (System Preferences>Sharing>Internet Sharing), and told the iPhone 3GS to connect, via Wi-Fi, to the iMac. We trained Wireshark on the built-in Ethernet card and told it to capture all traffic to and from the iPhone’s IP address.

Additionally, we turned Push notifications off (Settings>Mail, Contacts, Calendars>Fetch New Data>Off) to try to cut down on background chatter to other apps and the iPhone OS itself during the testing.

We tested each app twice: once for 30 seconds, and a second time for three minutes.

This method lets us look at the iPhone 3GS’s data usage on a Wi-Fi network. A drawback of this approach is that apps may behave differently on Wi-Fi than they do on a 3G network: maybe some apps throttle their data usage to suit the available network. Under good conditions, Wi-Fi is often faster than 3G, especially in places where the 3G network is congested, so these data transfer numbers may be higher than what is possible over your local 3G network.

There are other caveats as well: We’re not you. Each of us uses the iPhone differently. We’ve noted the things we did during the three minutes, to give you an idea of how we got these numbers.

Though we’ve turned off Push notifications, it’s possible that the iPhone OS, or some other Apple apps still need to talk to the Internet now and then. So, the data from our usage sessions may be affected somewhat by this traffic, if it exists at all.

Finally, some of these apps may store information in caches, so they don’t have to be reloaded each time. Some items won’t need to be fetched from the network if they’re already cached, saving on bandwidth.

Use this information to get a sense of what actions chug the data like a beer funnel, and what actions gently sip it like a fine wine.

The Tests

Facebook

The iPhone is great for checking Facebook while at work, especially in work places that are hostile to social networks: by tapping into the 3G network, you can get around the company firewall.

30 Seconds after launch = 72kB
We had just enough time to look at notifications, and read a few comments on friends’ threads.

3 Minutes after launch = 1.546MB
After reading more comments, we looked at a friend’s profile, looked at photos of her daughter, left a comment, checked out a local band’s schedule, and followed some links to blogs.

The photos are probably what made us use so much bandwidth.

Tweetie

There are a lot of apps out there that check Twitter; Tweetie is a capable, functional Twitter app that includes the ability to search for nearby users.

30 Seconds after launch = 32kB
We looked at a few tweets, and tweeted once.

3 Minutes after launch = 807kB
We loaded more screens of tweets, looked at mentions, messages, favorites, trending topics, and loaded updates from nearby users. Also followed links.

The links to other sites are what made the second session use so much more bandwidth than the first. We have a feeling if we’d kept it all within twitter, we’d have used a lot less data.

Maps

As they said on Saturday Night Live, "Google Maps is the best. Tru dat. Double true." That’s why the Maps app that comes with the iPhone uses Google Maps as its underlying technology.

30 Seconds after launch =19kB
In map view, we told Maps to find our location, then mapped directions to a location across the river.

3 Minutes after launch = 5.65MB
In map view, we told Maps to give us directions from Elmira, N.Y. to Philadelphia. We checked each step in the turn, and pondered the weird shape of the highway north of Scranton. Upon arriving in Philadelphia, we switched to satellite view to get a sense of what landmarks we might look for.

This is no surprise. The 19kB session was so small because the map for our location was already cached. It didn’t need to fetch many graphics to get us to the destination, only a mile away. On the other hand, We’d never looked at Philadelphia from this phone, so all of the graphics needed to come from somewhere.

Weather

In days past, people used to dial on copper landlines to a number at the phone company in order to get the latest weather forecast. The Weather app that comes with the iPhone just contacts Yahoo! instead.

30 Seconds after launch = 6kB
Weather loaded the current conditions and six-day forecast for the six cities we’d already set up the phone for. Then it sent and received nothing for the remainder of the session.

3 Minutes after launch = 309kB
We added another city, then decided to tap on the Y! icon in the bottom left, which loads a Yahoo! Search page for that city in Safari. We spent some time looking at news and events in Seoul, South San Francisco, and Elmira.

Once again, a web link pushes data usage up. See how easy it was?

YouTube

Millions of people use YouTube daily. The iPhone app downloads compatible versions of videos to your screen, if they’re available.

30 Seconds after launch = 109kB
We found that :30 was not enough time to get a video to play; the video we picked from the most recent uploads was very slow-loading. But, some data did transfer anyway.

3 Minutes after launch = 11.62MB
We watched three videos of glorious soccer playing.

Video is one of the big bandwidth-eaters, as you can see from how much data we caused to go all over the network. Do you remember when files of that size would have been segmented onto floppy disks and tied to carrier pigeons?

iTunes

The confusingly named iTunes app doesn’t play your music library like iTunes on your Mac does. Rather, it’s the iTunes store, and it lets you grow your library, no computer required.

30 Seconds after launch = 1.20MB
It took a while to load, then we listened to one song sample.

3 Minutes after launch = 14.42MB
We downloaded the free single of the week, and listened to a bunch of samples (sometimes not listening to the entire sample, but skipping to another track).

Wow. We’re honestly surprised that iTunes somehow managed to use more data than YouTube. Maybe it was because we were skipping around a lot; perhaps much of the data transferred for our 30-second samples went to waste.