ENUM stands for Telephone Number Mapping. Behind this abbreviation hides a great idea: To be reachable anywhere in the world with the same number. Not only that but also via the best and cheapest route. The general idea behind ENUM is to unify the international Public Switched Telephone Network (PSTN), with internet addressing. ENUM takes a phone number and links it to an internet address (URL or IP address) which is published in the DNS system, that can be used in Internet Communications. The owner of an ENUM number can thus publish where a call should be routed to via a DNS entry. What’s more, different routes can be defined for different types of calls – for example you can define a different route if the caller is a fax machine. ENUM does require the specific support from the phone of the caller.
You register an ENUM number rather like you register a domain. At present many registrars and VoIP providers are providing this as a free service.
ENUM is a new standard, and is not that widespread yet. Though it looks to become another revolution in communications and personal mobility.