What is the engine behind .Tel Technology?

The power of NAPTR

The Naming Authority Pointer (NAPTR) record is a powerful resource record type that holds a URI (Uniform Resource Identifier), which can identify arbitrary endpoints for any form of com-munication: telphony, VoIP, IM, email, etc. The record specifies the type of contact it represents and the contact itself. A NAPTR can even point to another domains with a set of records, in which case it is called a non-terminal NAPTR, NTN. In addition, a NAPTR has Order and Preference fields, which allow creation of sorted lists of contacts to convey messages like "If you cannot send a fax, send me an email" or "Don't call me on my cell phone when I'm overseas; use Skype instead". The full NAPTR packet content is de-scribed in RFC 3403 [4].  (.tel institute note#1)