Level 3 restored its peering connection with fellow ISP Cogent late on Friday, temporarily ending a standoff that had seen thousands of businesses suffer reduced Net and email usage.

Level 3 says its backdown is only an ad-hoc solution. "Because Internet users, apparently without notice from Cogent and through no fault of their own, have been impacted, Level 3 has, effective immediately, re-established a free connection to Cogent," the company said in a written statement. "In order to allow Internet users to make alternative arrangements, we will maintain this connection until 6:00am ET, November 9, 2005."

Level 3 said it is open to negotiating a new contractual arrangement with Cogent that will be equitable to both sides. Cogent has also indicated a willingness to resume negotiations with Level 3.

The stand-off between the two companies began Wednesday morning, when Level 3 terminated a "peering" arrangement through which it and Cogent exchanged traffic across their networks without charge. Peering is advantageous when both partners trade similar traffic volumes, but Level 3 maintains that it was carrying most of the load in its exchange with Cogent.

Level 3 says it warned Cogent in July that it would end the peering arrangement unless the two sides agreed on "alternative commercial terms", likely involving Cogent paying Level 3 to continue carrying its traffic. When Cogent ignored those notices, Level 3 carried through on its threat and cut Cogent off, leaving some customers on each vendor's network unable to reach certain sites that depend on the other vendor's network.

A Level 3 spokeswoman said last week that the company's Cogent de-peering was part of a more widespread evaluation of Level 3's peering agreements, a review that led it to renegotiate or end several other peering contracts. Only its Cogent de-peering, however, affected enough customers to prompt a noisy backlash against both Cogent and Level 3.