(Electronic NUMbering) A protocol from the IETF for converting a telephone number to an IP address and vice versa so that it can be resolved by the Internet's DNS system like traditional website domains. Primarily designed to strengthen voice over IP (VoIP) service, ENUM is expected to provide a one-stop directory for contacting people and services and to integrate the public telephone network (PSTN) with the Internet. See DNS, VoIP and VPIM.The E164 ARPA DomainENUM transforms a phone, fax or pager number into a dotted Internet address that is stored in the DNS system. For example, the fully qualified telephone number 1-215-555-1234 would turn into 184.108.40.206.220.127.116.11.1.2.1.e164.arpa. The digits are reversed because DNS reads right to left (the top-level domain such as .com in a URL is read first).Typing in a telephone number would resolve into a URL where the target could be a traditional phone, a VoIP phone or a Web service. ENUM records can hold attributes about a device such as whether it can receive a text message or is Internet capable. See E.164, RDF and XDI.
A standard (RFC 2916) issued by the Internet Engineering Task Force (IETF) for translating between PSTN and Internet addresses. ENUM translates between PSTN telephone numbers, as specified by the ITU-T in E.164, and Internet Protocol (IP) addresses, as specified for IPv4 in RFC 791 and IPv6 in RFC 2460. ENUM requires that both E.164 and IP addresses be registered with the ENUM Domain Name Service (DNS), which can be consulted by gateways that interconnect the two disparate networks. Thereby, a given call can traverse both the PSTN and the Internet or other IP-based packet network. See also DNS, E.164, gateway, IETF, Internet, IP, IP address, IPv4, IPv6, ITU-T, PSTN, RFC, and telephone number.