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What Does ENUM Mean?

ENUM is a term that springs up now and again, but what is it referring to and why is it something to pay attention to? ENUM stands for telephone number mapping. It is a simple four letter acronym representing a monumental idea: being able to use the same phone number no matter where in the world you are.

How it works

ENUM unifies the international public switched telephone network (PSTN) with internet addressing. This works by translating standard telephone numbers into internet addresses (URL or IP address). Servers that support ENUM will search any dialled phone number in the ENUM tree of the DNS to locate substitute ways to setup a call outside of the standard PSTN telephone line.

Types of ENUM

There are three types of ENUM:

  • Public User ENUM: This ENUM allows the end user to manage their own account and enter their own records into the ENUM registry.
  • Private Infrastructure ENUM: This type is used by a specific group without using the public domain. This group creates a domain name for each telephone number and links it to a uniform resource identifier (URI).
  • Public Infrastructure ENUM: This final type of ENUM is centrally managed by a National Number Administrator. This authority delegates a telephone number to a carrier, which in turn assigns the telephone number to an end user. The carrier maps telephone numbers to an internal network of addresses in order to enable call routing. This type of ENUM is the most protected as only service providers have access to the information.

Rules for ENUM numbers

The owner of each ENUM number has the ability to publish their number and choose rules for how the call should be routed. This could be one rule for a call from a fax machine and another from a phone. ENUM requires the specific support from the phone of the caller.

Registration of your ENUM number

An ENUM number is registered much like how you would register a domain. At present many registrars and VoIP providers are providing this as a free service. Registration needs to be done through a registration service such as Ripe with the standardized ENUM request form. This is then registered with the International Telecommunication Union, Telecommunication Standardization Sector, Telecommunication Standardization Bureau (ITU-T TSB). After this the number is registered and ready for international use.

New but growing standard

ENUM is a new standard and is not that widespread yet. Though it looks to become another revolution in communications and personal mobility. As more and more providers utilize it the mobility of workers and individuals alike will be greatly increased and costs will continue to decrease.

More information

The ENUM RFC 3953 standard
ENUM page at the ITU

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