MCI is more than two-thirds of the way through a conversion from circuit-based telephone service to voice over IP-based service in 51 of the largest cities in the U.S. The move would allow it to build the foundation for providing services such as video calling and multimedia services over phone lines, MCI announced Tuesday.MCI\u00a0is more than two-thirds of the way through a conversion from circuit-based telephone service to voice over IP-based service in some of the largest cities in the U.S., allowing the telecommunications company to build the foundation for providing services such as video calling and multimedia services over phone lines, MCI announced Tuesday.MCI, the new name of WorldCom, has deployed Nortel's Passport Packet Voice Gateways in 36 locations - including New York, Los Angeles, Houston, and Phoenix, Arizona -\u00a0since January, as well as Succession superclass softswitches. The company plans to install the VoIP networking equipment in 15 more locations by the end of June, said Rick Price, MCI's vice president of network engineering.Customers of MCI should notice no immediate difference in service quality, Price said, but they can expect new services to eventually be rolled out as part of what MCI is calling its\u00a0convergence strategy."It's like redesigning the airplane mid-flight," said Stephen Garcia, director of voice-over-packet marketing at Nortel.Garcia praised MCI for the aggressiveness of its IP rollout. MCI plans to have 25% of its voice traffic moving over the IP core network by the end of 2003 and all its traffic on that core by 2005, according to the company.MCI announced the plan to go into 15 new markets Tuesday at the SuperComm trade show in Atlanta. The move to an IP core makes sense, Price said, because that's the direction voice services will be headed in the future. "IP is the dominant data communications protocol and well be the basis for all communication services in the future," Price added.MCI sees services such as application collaboration becoming available on the IP network, as well as video calling and multimedia services, Price said. MCI's deployment will be the largest commercial deployment of Nortel's\u00a0voice over IP equipment in the world, according to Nortel.As part of its transition to voice over packet, MCI gradually is replacing Nortel's DMS circuit switches with Succession Communication Server 2000 superclass softswitches. A superclass softswitch allows circuit-to-packet migration, including local, tandem and long distance capability on a single platform, plus full business and residential telephony service sets, third-party interoperability, and carrier-grade scalability.