Microsoft's online services hit by outage

Several of Microsoft's online services suffered an outage last night but are reportedly all back up at this point.

The company's Office 365, Hotmail, SkyDrive, and various Windows Live services were down throughout the world for a period of around three hours. Microsoft acknowledged the outage late yesterday in its Inside Windows Live blog and on its Office 365 Twitter feed and said that it was working to resolve the issue.

After a couple of hours of investigation, the company pinned the cause on a DNS (Domain Name System) issue and said that it was starting to see intermittent recovery in various regions of the world. DNS is responsible for translating domain names, such as microsoft.com, into IP addresses, such as 207.46.170.123, so that Internet traffic can be delivered to the right location.

"Still working to restore service," tweeted Microsoft at around 11:00 p.m. PT. "Preliminary root cause suggests a DNS issue, though we're still working hard to restore."

An earlier update at the Inside Windows Live blog at 9:45 p.m. PT incorrectly stated that all services had been restored at that point but corrected itself about an hour later, acknowledging that customers were still experiencing connection problems.

After propagating its DNS fix throughout the world, Microsoft tweeted around midnight that it believed service had been restored for all Office 365 customers (and presumably for customers of Hotmail and the other affected online services).

Providing further details, a Microsoft representative told CNET that "on Thursday, September 8th at approximately 8 p.m. PDT, Microsoft became aware of a Domain Name Service (DNS) problem causing service degradation for multiple cloud-based services. A tool that helps balance network traffic was being updated, and for a currently unknown reason, the update did not work correctly. As a result, the configuration was corrupted, which caused service disruption. Service restoration began at approximately 10:30 p.m. PDT, with full service restoration completed at approximately 11:30 p.m. PDT. We are continuing to review the incident."

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This is hardly the first time the company has been hit by such an outage of its cloud services. Office 365 went offline briefly in mid-August, less than two months after it debuted in late June, according to the BBC News. And about a year ago, the company's online hosted versions of Exchange and SharePoint suffered at least three separate outages over the course of almost two weeks, which Microsoft blamed on a change to its network infrastructure.

But Microsoft certainly isn't alone.

Google has also seen its share of downtime. Just this past Wednesday, Google Docs was offline for about 30 minutes. In May, the company's Blogger service was unavailable for the greater part of a day. And in 2009, a host of Google services went down briefly throughout the world.

Early last month, many Yahoo Mail users around the world were unable to access the service for almost a day.

Amazon, too, has experienced outages over the past year with its Elastic Compute Cloud (EC2) service, which hosts the Web sites of many major companies. One disruption in April affected such customers as Quora and Reddit, while another one last month took Netflix, Foursquare, Quora, and Reddit offline.

Updated on 9/10 at 4:15 a.m. PT with more detailed statement from Microsoft.