Access to Microsoft's Hotmail, Messenger and Passport services as well as some other MSN services was cut for more than an hour after AT&T made routing changes on its backbone.
The changes were made in preparation for the addition of capacity between AT&T and Microsoft that is meant to improve access to the services hit by the outage, said Adam Sohn, a spokesman for Microsoft. "We are doing some work with AT&T to add more capacity and better route traffic between AT&T's network and Microsoft's services," he said.
"AT&T made some changes in preparation for this and the effect was that traffic was incorrectly directed causing some of our services to become unavailable to 40% of Internet users at peak. Microsoft services were up and running but people could not get to them."