ENUM is a new registry service that combines telephone numbers and the Domain Name System to simplify the way that VoIP calls (telephone calls made over the Internet) work. It allows more VoIP calls to be connected directly over the Internet, for no charge, rather than via the traditional PSTN network.
ENUM translates a telephone number into a domain name. This allows users to continue to use the existing phone number formats they are familiar with, whilst allowing the call to be routed using DNS. This makes ENUM a quick, stable and cheap link between telecommunications systems and the Internet.
Fig.1 Diagram showing relationship between Telecommunication companies,
businesses and VoIP technologies.