In the latest expression of network operator angst at being relegated to a bit pipe for VOIP traffic, Washington-based ISP Clearwire Inc. has “port blocked” traffic to at least one Vonage Holdings Corp. customer, Vonage believes.

No one was hurt, nobody lost any customers, and Vonage has not cried foul; but the event, first reported here, may be an early dust-up in a conflict of interest that will only grow with the popularity of consumer VOIP.

Consumer VOIP providers such as Vonage make money by delivering their service over the last-mile networks of ISPs. ISPs do not share in that wealth. On the contrary, operators complain that VOIP service demands large amounts of bandwidth and can slow down the overall performance of their networks.

“As much as I want to see VOIP survive and thrive, I also don't want to bear the additional cost of my customers choosing to use a competitor's VOIP service over my own,” says Greg Boehnlein, who operates Cleveland, Ohio-based ISP N2Net.

“Without control of the last mile, we're screwed,” Boehnlein says, “which is why I can identify with Clearwire's decision and say ‘more power to them’.”

Meanwhile, VOIP providers like Vonage have insisted that voice services should be allowed to move over host networks untaxed and unencumbered.

Vonage CEO Jeffery Citron tells Light Reading that port blocking VOIP service is tantamount to censorship. "If they can examine the packets and tell that its VOIP traffic, then what are they going to do next?" Citron asks. "How long will it be before they are looking at the actual content and blocking what they don’t like?"

And so far the Federal Communications Commission (FCC) has been sympathetic to Citron’s case. The agency took only three weeks to stop regional carrier Madison River Communications from blocking Vonage’s traffic, as well as making it pay a $15,000 fine and agree to play nice from now on.

But some ISPs see Vonage’s refuge-seeking at the FCC and in the courts as anti-competitive. “Oh, yes, we should run screaming to nanny government and get permission to stop Clearwire if we don’t like what they do,” says David McClure, president and CEO of the U.S. Internet Industry Association, mocking Vonage.

McClure believes that operators have the right to dictate what types of traffic flow in and out of their networks. “Some people have the idea that if you go out and invest and build technology somehow you should just give it away to anybody who wants it,” McClure says.

ISPs can easily block VOIP at the edges of their networks by defining an access list that denies such traffic. It is the same method used to block inbound MS-SQL attacks.“We are still under investigation with Clearwire,” says Vonage VP of corporate communications Brooke Shulz. “We are aware of a couple things that happened, but they suddenly went away, so we are still trying to figure out what happened.”

In those cases, Vonage engineers simply changed the customer’s VOIP port number and the service was restored, Shulz says. The Clearwire case is just one of several run-ins Vonage has had with ISPs around the country, she said.

Clearwire and its lawyers seem to have anticipated problems with consumer VOIP traffic long before the Vonage incident. The ISP’s Terms of Use page reads: “You acknowledge and agree that the Service is not a telephone service . . . the Service is subject to different regulatory treatment than telephone service.”

In its Acceptable Use Policy, Clearwire states: “To protect its customers and its network Clearwire may, without limitation, block and allow traffic types as we see fit at any time.” This, the policy reads, can be applied to customers who “continuously” use high bandwidth applications such as file sharing and audio/video streaming.

These terms were probably written to give Clearwire the right to cap the amount of peer-to-peer traffic generated by its customers when using file-sharing services to download movies and music. Many P2P protocols dynamically shift port numbers to make it difficult for ISPs to identify and thus control this type of traffic.

Clearwire’s argument that VOIP traffic uses too much bandwidth is only half the picture. Clearwire’s own voice service, which is now being built for it by Bell Canada, is likely to consume just as much bandwidth as Vonage and its ilk. The difference of course is that Clearwire will feel a lot better about expending bandwidth on a VOIP service that will drive revenue.

“No matter how the press may spin it, it's Clearwire's investment money that built their network. What they allow people to do with it is their business,” N2Net’s Boehnlein says.

“If they decide to block VOIP, so be it; consumers will vote with their feet.”

Clearwire did not respond to requests for comment for this story.

— Mark Sullivan, Reporter, Light Reading