A bandwidth spat opened a rift on the internet last week, cutting off web traffic between two of the world’s larger bandwidth providers: U.S.-based Cogent Communications, and Swedish telecommunications giant TeliaSonera.

The two companies participate in a common arrangement on the internet called peering, which permits traffic to flow between major bandwidth providers by agreeing to trade roughly equal amounts of data amongst each other. When that connection is severed, called de-peering, customers from one network are unable to communicate with the other, unless they can route around the split via other, third-party networks.

According to Cogent CEO David Schaeffer, TeliaSonera peered data selectively and refused to upgrade bandwidth at some of the companies’ peering connections, causing traffic to take long, winding routes around the internet and saturating peered connections’ pipes.

“Some traffic flow was impeded and some traffic was redirected further than it needed to go,” said Cogent spokesman Jeff Henrikson. “They weren't responding to requests to comply with our contract, and we weren't left with much alternative but to terminate the contract.”

Initially, customers wanting to reach the other providers’ network were able to do so, utilizing networks from Verizon, AT&T and Level 3 Communications – but that only worked for about 12 hours, after which communications between the two mysteriously stopped.

Earl Zmijewski of internet intelligence firm Renesys says that the split is the result of one of three different outcomes:

• Cogent stopped accepting routes to Telia from outside networks.
• Telia stopped accepting routes to Cogent from outside networks.
• Outside networks (Zmijewski names Verizon) stopped accepting traffic between the two.

Speaking to the Washington Post, Cogent CEO David Schaeffer denies the fact that the loss of routes had anything to do with Cogent, instead speculating TeliaSonera likely refused to pay other providers for traffic.

A representative for TeliaSonera, when contacted by the Washington Post, refused to comment on Schaeffer’s speculations but said that the two companies were in negotiations to resume connections – but that it wouldn’t consider re-peering until “TeliaSonera receives the compensation Cogent owes us.”

Schaeffer says that his company’s expansion into Nordic territories – TeliaSonera’s home turf – may have something to do with the ongoing spat and TeliaSonera’s alleged lack of cooperation.

“We've become much more aggressive,” said Schaeffer, “as we have expanded our network about four months ago in Norway and Finland.”

De-peering disputes often devolve into a game of “chicken,” where the two companies try to completely cut off each other’s traffic; the onus of response is left to whichever company has the largest customer uproar when their networks stop working and websites become inaccessible.

However, authorities on the matter are failing to find real-world examples of disruptions caused by the Cogent/TeliaSonera dispute: “I don't have any juicy examples,” wrote Zmijewski, noting that his lack of examples is both good and bad: bad, because only through big examples would the two companies be forced to settle their differences; but good, because it seems that the de-peering dispute is having little impact on the greater internet.

Zmijewski was able to find one example, though: “Martha Stewart Living is [a single-homed network] behind Cogent … If you go to Telia's looking glass as of the time of this posting, you cannot get to Martha's network. As far as Telia is concerned, Martha doesn't exist.”

“Does this mean that the Swedes are deprived of the pleasure of buying Martha's wares and sending her email?” asked Zmijewski. “Not at all. Her web site is hosted by Savvis and a customer service email address points to AOL. But if Martha's parole officer allows her to visit Scandinavia any time soon, she won't be able to reach her corporate network.”

Given that the majority of Cogent’s clients are large businesses and ISP’s with tens-to-hundreds of thousands of customers, it’s likely that Cogent’s clients are simply routing around the rift on their own, using backup connections from other bandwidth providers.