NTT Communications Corp. plans to start providing a marketplace on the Internet for companies to sell a broad range of products, from financial services to music and game software, company sources said Monday. NTT Communications, a domestic and international long-distance carrier, plans to start what will be the first comprehensive electronic trade service by the end of the year, the sources said. NTT Communications will oversee identity authentication in order to prevent fraudulent use of the service, they said.Users of the service will have to install a terminal adapter at home and will have to insert an IC card to confirm their identity. Once they gain admission to the service, users will not be required to input credit card information every time they make a purchase.