  ENUM marks either the convergence or collision of the public telephone
network with the Internet. ENUM is an innovation in the domain name system
(DNS). It starts with numerical domain names that are used to query DNS name
servers. The servers respond with address information found in DNS records.
This can be telephone numbers, email addresses, fax numbers, SIP addresses, or
other information. The concept is to use a single number in order to obtain a
plethora of contact information.
  By convention, the Internet Engineering Task Force (IETF) ENUM Working Group
determined that an ENUM number would be the same numerical string as a
telephone number. In addition, the assignee of an ENUM number would be the
assignee of that telephone number. But ENUM could work with any numerical
string or, in fact, any domain name. The IETF is already working on using E.212
numbers with ENUM. [Abridged]
