'Unlimited' worries

New mobile calling plans are driving network-monitoring requirements

In March, Sprint led a coup in the wireless industry: It launched an “unlimited everything” plan for $100 per month, which not only gives its customers all of the voice minutes and text messages they can consume, but also unrestricted access to the mobile data network. The data aspect of the plan raises an interesting question: Can operators really support unfettered access to their data networks without crashing them?

“The one application that scares operators the most is video — Slingbox and YouTube on the phone,” said Cam Cullen, director of product management for Allot Communications, which supplies deep packet inspection platforms to operators. “There is not a lot of room on the same cell for more than two or three people using video at once. Video isn't choking the operators' networks just yet, but it's a growing concern as more and more people start using it.”

Allot and other DPI companies have been turning their attention to the wireless industry to tackle increasing concerns over bandwidth intensive applications such as peer-to-peer (P2P) file sharing. As its name implies, DPI looks at the IP packets crossing the network, identifying the nature of the data and the person using it. That technology can be used to prioritize certain traffic — say an operator's portal video service over a third party's — and it can be used to identify problem users.

What to do about those problem users, though, is tricky. While Cullen said Allot has sold its DPI platform to a dozen network operators, most of them are using the solution to shape their policies and pricing plans. Almost none of them are using it to actively shut down an identified bandwidth hog or prohibit offending applications.

“There is still concern about Net neutrality,” Cullen said. “At the end of the day, you won't see operators actively blocking these applications unless they're illegal applications.” What you will see are more fair-use policies that allow customers to access any application but charge them varying rates for such access, Cullen said. For instance, a customer could buy a video-streaming plan that allows unlimited access to video, but not to P2P or voice over IP.

The problem with that type of approach is that it assumes high-bandwidth applications are bad for the network. According to Mike Schabel, general manager for the Alcatel-Lucent venture Aware, a low-bandwidth application such as push e-mail actually consume far more network resources than a high-bandwidth one. The signaling traffic that push e-mail or other constantly “pinging” applications create is constantly opening channels to the radio access network, which, while transmitting very little data, sucks up airtime resources.

Schabel performed a study on an unnamed operator's network and found that push e-mail didn't even register as a proportion of overall bandwidth consumed over a 24-hour period. Conversely, browsing and P2P traffic accounted for more than half of all bandwidth used. But when Schabel analyzed the impact those apps had on airtime, their roles were entirely reversed. Browsing's impact on airtime shrunk considerably, and P2P became a non-factor. The reason, Schabel said, is that P2P uses the network very efficiently despite its bandwidth demands — a P2P app opens a channel, sends or receives a file and then shuts down that channel.

“I don't think that operators know it's bad — they just think it's bad,” Schabel said of P2P traffic. “The truth is that a corporate [virtual private network] with an open connection over the network can be far more damaging than a peer-to-peer application.”

Schabel said he isn't implying that P2P is good while e-mail is bad for the network. Multiple people simultaneously engaging in file-sharing on the same sector will drain capacity resources, just as multiple BlackBerrys simultaneously signaling their servers will drain airtime resources. The key to shaping network policies is to analyze how each application is used on the network — not just how much capacity it consumes, he said.

“It's become extremely important to understand how each individual subscriber and application is impacting the network,” Schabel said. “It's not just simply a matter of bandwidth.”