1 EXHIBIT 21.1 SUBSIDIARIES OF THE REGISTRANT STATE OR OTHER JURISDICTION OF OTHER NAMES INCORPORATION UNDER WHICH OR SUBSIDIARY NAME OF SUBSIDIARY ORGANIZATION DOES BUSINESS TYPE OF ENTITY ------------------ ------------ ------------- -------------- Atlantic States Microwave Transmission Company Nevada None Corporation Central States Microwave Transmission Company Ohio None Corporation Infotel Europe N/A European Joint Venture IXC Broadband Services, Inc. Delaware None Corporation IXC Business Services, LLC Delaware None Limited Liability Company IXC Carrier, Inc. Nevada None Corporation IXC International, Inc. Delaware None Corporation IXC Internet Services, Inc. Delaware None Corporation IXC Leasing, LLC Delaware None Limited Liability Company IXC Long Distance, Inc. Delaware None Corporation IXC-One Acquisition Corp. California None Corporation Link Net International, Inc. Delaware None Corporation Marca-Tel S.A. de C.V. Mexico None Corporation MSM Associates, Limited Partnership Delaware None Limited Partnership Mutual Signal Corp. New York None Corporation Mutual Signal Corporation of Michigan New York None Corporation Mutual Signal Holding Corporation Delaware None Corporation Pisces Acquisition Corp. Delaware Corporation Progress International, L.L.C. Texas None Limited Liability Company Rio Grande Transmission, Inc. Delaware None Corporation Switched Services Communications, L.L.C. Texas None Limited Liability Company Telcom Engineering, Inc. Texas None Corporation Telecom One, Inc. Delaware None Corporation Tower Communication Systems Corp. Ohio None Corporation UniDial Communications Services, LLC Kentucky None Limited Liability Company U.S. Advantage Long Distance, Inc. Texas None Corporation West Texas Microwave Company Texas None Corporation Western States Microwave Transmission Company Nevada None Corporation European Joint Venture England N/A Joint Venture