ENUM — Phone numbers on the Internet

The problem of a single identifier for multiple communication services can be solved with different approaches. One simple approach is the ENUM system developed by the IETF (Internet Engineering Task Force), using existing E. 164 telephone numbers, protocols and infrastructure to point to different services available under this identifier. The technical aspects of the underlying protocols and the administrative aspects of the distributed database used — the domain name system — are presented. This includes the related activities in ITU and ETSI and possible national implementations.