WorldCom, which runs the major backbone network that routes traffic over the Internet, said it suffered a widespread outage on Thursday that cut off some businesses for most of the work day and slowed Web access for others.
The network problems, which began at 8 a.m. EDT, affected about 20 percent of WorldCom"s Internet customer base, the company said. Service was restored before 5:15 p.m. EDT, when the company released a statement.
The outage disrupted service to corporate networks and millions of computer users, misdirected electronic mail, and slowed Internet service for others across the United States and worldwide, analysts said.
Based on a preliminary investigation, WorldCom blamed the outage on problems with a "route table," or software map that directs traffic to the proper destination. The company declined to identify the route table manufacturer.
"There were some people who were literally unreachable. If you subscribe directly to WorldCom"s service, you couldn"t get onto the Internet," said Peter Salus, chief knowledge officer at Matrix NetSystems, based in Austin, Texas.