Method and apparatus for correlating a unique identifier, such as a pstn telephone number, to an internet address to enable communications over the internet

System comprising: a directory service (DS 12) residing on a data network (10) containing a unique identifier unrelated to the Internet and associated addresses, wherein the unique identifiers are at least one selected from the group consisting of telephone numbers, random numbers, codes of personal identity, social security numbers, pronounced registered names, voice prints, fingerprints and retina scans, characterized in that: at least one unique identifier is associated with multiple addresses Internet systems for different Internet-enabled communications; and the directory service includes means processors are operable to determine, in response to a conversion request containing a unique identifier, a conversion of the unique identifier in one of the many Internet addresses based on information contained in the application to determine which Internet address is associated with a given communications system.