DPI: The good, the bad, the stuff no one talks about

The problem is that the non-tech industry associates DPI with what Comcast and its vendor, Sandvine, were caught doing in 2007 – essentially blocking peer-to-peer traffic that can clog up networks. The traditional DPI approach had been to detect P2P traffic such as BitTorrent and set network policies such that it couldn’t absorb massive amounts of bandwidth during peak congestion times. That would slow down P2P connections during peak hours but enable them to stay connected, Malan said.

What Comcast and Sandvine did was detect P2P traffic and then send fake packets from each of the two end points that indicated the connection was being shut down, Malan said. Comcast and other cable operators have been accused of blocking P2P traffic during non-peak times as well.

Both Comcast and Sandvine have backed away from that use of DPI, and both have done major penance for the prior acts. Comcast has announced a system-wide protocol-agnostic network management technique to address congestion and network management without singling out P2P traffic and is collaborating with BitTorrent to address congestion issues related to P2P. The cable giant has tried to get on top on the issue by leading an effort to develop a P2P users’ bill of rights, and it has done much to make its user policies more obvious and understandable.

Sandvine this spring announced FairShare, a suite of traffic optimization products that build on DPI but take a broader approach designed to guarantee all types of users fair access, said Tom Donnelly, cofounder and executive vice president of Sandvine. “Applications are changing all the time, and the network infrastructure has to keep up with that,” Donnelly said. “What network operators want to do is create an infrastructure where the broadest mix of applications and users can co-exist, but there has to be the understanding that not all bits are equal. Latency-sensitive bits have to be treated differently.”

But the Comcast/Sandvine episodes, and others, have cast DPI as a means for service providers to learn a lot – maybe too much – about what their customers are doing and to use that information in potentially harmful ways. As a result, most service providers are just not talking publicly about what they are doing with DPI. For this story, neither AT&T nor Verizon wanted to discuss their use of the technology much beyond a generic description of what DPI could do.

“People are talking and starting to embrace the technology in that way,” Davis said. “But there is still enough of a backlash from the more ham-fisted use of technology that lawyers within the service providers have created a human wall with rules and regulations around what can be discussed publicly.”

That doesn’t mean there’s nothing happening behind the curtains, however. Part two of this series will look at what that might be.