MCI has had more ups and downs than a telephone repairman's oscilloscope. A subsidiary of Verizon Communications, which completed its acquisition of MCI in early 2006, the company was once the #2 long-distance operator in the US and manager of one of the world's largest communications network systems. The MCI network is one of the largest carriers of international voice traffic and a leading Internet protocol backbone system. Formerly WorldCom, the company revived its old MCI name in hopes of putting the past behind it in an effort to recover from accounting fraud by former executives. In 2004 it emerged from bankruptcy and moved its headquarters from Mississippi.