ENUM means the application of the Domain Name System to convert telephone numbers to internet addresses.

An ENUM link enables you to make SIP calls with ENUM number resolution via the Internet.

A user of a SIP phone is thus able to investigate the SIP address automatically using only the telephone number of the called party, and to convert the number into the SIP address. The called party can then be reached over the IP network in spite of using a 'normal' phone number. This postulate that the called party is registered at ENUM.