That has happened when negotiations break down and two networks refuse to trade traffic, directly or indirectly. Back in 2005, Level 3 got into a battle with Cogent Communications, another huge global network. One day, Level 3 got fed up with Cogent’s refusal to pay it the money Level 3 felt it was due, so the company simply stopped exchanging Internet traffic with Cogent. Suddenly, Level 3 customers and Cogent customers couldn’t reach each other’s Web pages—unless they had other ways of hooking in to the Internet.
The Internet was soon alight with angry customers from both companies. Many declared they wouldn’t pay for partial Internet access. Two weeks later, Level 3 essentially caved, as the two companies agreed to trade traffic at no cost to either party. (This is known in the trade as “settlement-free peering.”)
In 2008, two other ugly depeering battles flared up. The first cut off much of Scandinavia from many U.S. websites for two weeks. The second severed full Internet access to major U.S. and Canadian universities, the state government of Maine, the U.S. court system, and millions of Sprint mobile customers. That fracture lasted three days.
Big networks abide by different peering policies of their own design, but AT&T’s and Verizon’s are typical. Verizon, for instance, insists that settlement-free peers send and receive roughly the same volume of traffic: the ratio may not exceed 1.8 to 1 in either direction. It’s an odd tradition, on its face, but it’s based on the assumption that traffic should be balanced across networks over time. If a network wants to send Verizon substantially more traffic than it receives from Verizon, then Verizon makes it pay. And even if a network receives more traffic from Verizon than it sends out, then Verizon also can make it pay for allowing the imbalance. “No one has come up with a rigorous way of measuring value,” Odlyzko says.
Now the industry’s tradition of insisting on balanced traffic flows is smacking into the huge growth of Netflix and other video services from companies such as Apple and Amazon. Video downloads—huge files streaming in one direction—quickly throw traffic ratios out of whack. In the past, depeering has proven to be so painful for both sides that the companies involved quickly find a way to heal the breach. But it’s possible the flood of video surging onto the Internet will undermine the global network’s tendency toward peace.