‘Peering’ Into AOL-MSN Outage

The outage that barred AOL subscribers from Microsoft Web sites this week hasn’t reoccurred, but the tech titans remain unable or unwilling to pinpoint the cause.

That has to be less than reassuring news for millions of shared customers — those who use AOL’s network to get online to Microsoft’s MSN content portal and Hotmail e-mail.

Statements from the companies shed little light on the breakdown.

AOL has restored network connectivity “strictly on a short-term basis” and will work with Microsoft on a “longer-term solution.” Microsoft has “no further information . . . regarding the cause of any access issues for specific ISPs.” Level 3 Communications , which provides a backbone link between the two companies, declined comment.

Early on, several theories were floated, including routing changes by AOL, maintenance issues at Microsoft, or a combination of the two.

Some industry watchers believe the problem shows signs of dispute over peering agreements — deals between Internet service providers to create a direct link to route each other’s packets rather than pay a third-party network service provider for transport.

But such agreements only make sense if the amount of traffic sent to a partner’s network is roughly equal to the amount of traffic sent back. When it’s not, one ISP may ask for money or additional transit as compensation for the extra strain on its systems.

That may have been the case this week, one source familiar with the situation said. If correct, it wouldn’t be the first time AOL was involved in a peering contract dust-up.

In January, AOL wanted to charge Cogent Communications approximately $75,000 per month to keep their peering relationship intact. A Cogent spokesman declined to discuss AOL.

At the time, Cogent said it sent to AOL three times as much traffic as it received. AOL said that meannt Cogent did not have parity with AOL, and sought payment. Cogent argued that while it sent a lot of traffic through AOL it was local, whereas AOL’s traffic typically travels long distances on Cogent’s network, costing Cogent more.

In the end, Cogent found an alternate way to reach AOL customers, a source said.

While AOL may be the highest profile ISP to play hardball over the pacts, it certainly isn’t the only one. There have been disputes involving others dating farther back.

Two years ago, Cable & Wireless dropped its peering agreement with struggling backbone provider PSINet. The cancellation left C&W users unable to access IP addresses on the PSINet network and vice versa.

A short time later, the two companies struck a deal to restore service, but the incident exposed the downside of peering agreements — the fact that customers depend on good relations between rival network operators.

AOL wouldn’t comment on a peering contract dispute as a possible cause of this week’s MSN freeze. Microsoft said it made “no changes to its services or network infrastructure.”

Regardless of whether the problems were peering-related, AOL subscribers in the United States and United Kingdom who were left without access to Microsoft sites for a day-and-a-half this week weren’t happy.

A spokesman for AOL’s high-speed Road Runner Internet service didn’t have an exact number of calls to its customer service center, but conceded that “complaints were running faster” than normal.

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