Level 3 Communications Inc. (Nasdaq: LVLT)and Cogent Communications Group Inc. (Amex: COI) have ironed out their peering differences and will continue to exchange Internet traffic on a settlement-free basis, the companies said Friday.

The modified agreement contains new commitments from each party with respect to the “characteristics and volume of traffic to be exchanged,” the statement says. (See Level 3, Cogent Make Up .)

“The agreement calls for the equitable exchange of traffic, and if it becomes disproportionate, there is a penalty if it’s not remedied,” Cogent CEO Dave Schaeffer told Light Reading today. (See Internet Peering on Thin Ice? )

The two wouldn’t disclose specific traffic metrics requirements in the agreement. Level 3's original complaint, which led to the well publicized October 5 de-peering, was that Cogent was sending a disproportionate amount of Internet traffic over its network, costing Level 3 money.

The renewed agreement also contains commitments from both companies to give each other, and their respective customers, a notice period “of finite length” before de-peering in the future.

Level 3's action on October 5 left millions of users on both networks without access to the full Internet. (See Level 3 Tweaks Cogent.) Shortly afterward, Level 3 turned the connection back on and set a November 9 deadline for the two operators to reach terms, or for Cogent to find another peering arrangement elsewhere. (See Cogent: King of Ports .)

The two sides blamed each other for the meltdown at the time, but cooler heads have prevailed, and Level 3 CEO Jim Crowe even apologized to customers of both companies during his company's earnings call last week.

“During the quarter, we modified the nature of a number of relationships with the goal of making sure that the agreement remained equitable to both sides; we remain committed to this goal,” Crowe said. “In one instance this quarter, a number of Level 3 customers and Cogent customers were hurt as we pursued this strategy.

“I apologize to both sets of customers. In addition to achieving the contractual goal with interconnecting carriers, we recognize that we have an obligation to customers of the Internet, and in this instance we contributed to letting them down.”

Crowe’s comments were a departure from Level 3’s earlier, somewhat more defiant tone. Meanwhile, as the information rolled out about how one of the biggest disruptions in the history of the Internet actually occurred, some were surprised and alarmed that it could happen so easily.

“If Crowe knew what was going on behind the closed peering doors, and what the fallout could potentially have been, it would not have gone down that way,” says Hunter Newby of telx.

“CEOs don’t like to apologize," Newby says. "Good for him for doing so, but it could have been avoided.”

“I hope that any other major provider will take a long, hard look at what happened and really think before disrupting the Internet in any way,” Cogent’s Schaeffer says. (See Slowdowns Smack Level 3, Verio.)

— Mark Sullivan, Reporter, Light Reading