Sprint-Nextel has decided to sever its Internet connection with Cogent, another US-based Internet service provider, according to a statement from Cogent.

Internet health data supplied by Keynote Systems indicates that Cogent and Sprint are no longer exchanging traffic.

As a result, it is no longer possible for many Sprint customers and Cogent customers to directly communicate across the Internet.

The two ISPs are currently engaged in litigation over their exchange of Internet traffic, so-called peering. In shutting down the peering between the two, Sprint violated a contractual obligation to exchange Internet traffic with Cogent on a settlement-free peering basis, according to Cogent.

The actual reasons for the row remain sketchy. Cogent staff in Europe wouldn't comment further, passing questions to the company's legal team in Washington. Sprint couldn't be reached for comment.

This isn't the first time Cogent has rowed with another carrier over Internet peering with another carrier. Back in 2005 it was involved in a similar dispute with Level 3, which also decided to shut down communications with Cogent. In the end the two agreed on what they called a "modified" version of their original peering arrangement, which enabled the two providers to directly connect their networks and exchange Internet traffic across them without charge.

Earlier this year it was also embroiled in a battle with Swedish carrier TeliaSonera. That time it was Cogent that cut communications. They also settled their differences.

The dispute is unlikely to have an effect on the Internet as a whole, according to Kurt Erik Lindqvist, CEO at Netnod, which handles peering between carriers in Sweden.

In the short term, Sprint and Cogent costumers are stuck in middle, but in the end Lindqvist thinks they will be forced to work out their differences. "It's usually a question of who chickens out first," he said.

Three days into the previous standoff, Level 3 backed down and restored its peering connection to Cogent.

Carriers typically row over peering when they are unhappy with the amount of data traffic each carrier sends to the other, something usually covered by the peering agreement, according to Lindqvist. He doesn't know if that is the case here.

The conflict with TeliaSonera had to do with the cost for upgrading a peering point in the U.S.