What is Enum?

One of the principle elements of a future voice over Internet (VoIP) world is called the Enumbering, or Enum, initiative. Simplistically, it is a means of mapping phone numbers to Internet addresses, in the same way that domain names are mapped via the domain naming system (DNS).

It will enable networks to know where you can best be contacted, so re-routing calls as necessary via fixed line, mobile, Web etc – or even to translate a phone call into a voice message and attach it to an e-mail for forwarding.

The technology is complex, but as complex is how the technological and regulatory intersection of the Internet and the Public Sector Telephone Network (PSTN) is handled – including whether telephone numbers (of which there are already billions in place and which are language neutral) or Internet style addresses (using existing styles of Uniform Resource Indicators, or URIs) will be the optimum medium.

Enum is a protocol defined by the Internet Engineering Task Force (RFC 3761), rooted in a specific public part of the DNS, that is one way of addressing calls that pass from one network service to another. While a number of VoIP public services are already up and running (such as the European-based Skype), there are significant international issues impacting the way regulation is handled between states.

The International Telecommunication Union – the UN body through which governments and the private sector coordinate global telecom networks and services  - is working with the IETF to resolve outstanding issues, with a view to producing a recommendation in May 2005.

The benefits of converging voice and data have been apparent for a number of years. Now the technology has well and truly caught up with the concept – with considerable financial and operational benefits available to those who make the move.

Useful links for more information: <www.itu.int/osg/spu/enum>; <www.ietf.org/html.charters/enum-charter.html>; <http://www.itu.int/ITU-T/inr/enum/trials.html> (information about enum trials in various countries). For information on SITA's VoIP services, go to <http://www.sita.aero/>.