Combined User and Infrastructure ENUM in the e164.arpa Tree
RFC 5527

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Network Working Group                                        M. Haberler
Request for Comments: 5527                                           IPA
Category: Informational                                         O. Lendl
                                                                 enum.at
                                                              R. Stastny
                                                            Unaffiliated
                                                                May 2009

      Combined User and Infrastructure ENUM in the e164.arpa Tree

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
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Abstract

   This memo defines an interim solution for Infrastructure ENUM in
   order to allow a combined User and Infrastructure ENUM implementation
   in e164.arpa as a national choice.  This interim solution will be
   deprecated after implementation of the long-term solution.

Haberler, et al.             Informational                      [Page 1]
RFC 5527         Combined User and Infrastructure ENUM          May 2009

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Interim Solution ................................................3
   4. The Algorithm ...................................................4
   5. Determining the Position of the Branch ..........................5
   6. Transition to the Long-Term Solution ............................6
   7. Examples ........................................................7
   8. Security Considerations .........................................8
   9. Acknowledgments .................................................9
   10. References .....................................................9
      10.1. Normative References ......................................9
      10.2. Informative References ....................................9

1.  Introduction

   ENUM (E.164 Number Mapping, [RFC3761]) is a system that transforms
   E.164 numbers [E164] into domain names and then queries the DNS
   (Domain Name Service) [RFC1034] for NAPTR (Naming Authority Pointer)
   records [RFC3401] in order to look up which services are available
   for a specific domain name.

   ENUM, as defined in RFC 3761 (User ENUM), is not well suited for the
   purpose of interconnection by carriers and voice-service providers,
   as can be seen by the use of various private tree arrangements based
   on ENUM mechanisms.

   Infrastructure ENUM is defined as the use of the technology in RFC
   3761 [RFC3761] by the carrier-of-record (voice service provider)
   [RFC5067] for a specific E.164 number [E164] in order to publish a
   mapping of this telephone number to one or more Uniform Resource
   Identifiers (URIs) [RFC3986].

   Other voice service providers can query the DNS for this mapping and
   use the resulting URIs as input into their call-routing algorithm.
   These URIs are separate from any URIs that the end-user who registers
   an E.164 number in ENUM may wish to associate with that E.164 number.

   The requirements, terms, and definitions for Infrastructure ENUM are
   defined in [RFC5067].

   Using the same E.164 number to domain mapping techniques for other
   applications under a different, internationally agreed-upon apex
   (instead of e164.arpa) is straightforward on the technical side.
   This process of defining the Dynamic Delegation Discovery System
   (DDDS) [RFC3401] application for Infrastructure ENUM is defined in
   [RFC5526].  This is the long-term solution.

Haberler, et al.             Informational                      [Page 2]
RFC 5527         Combined User and Infrastructure ENUM          May 2009

   This document presents an interim solution for Infrastructure ENUM
   and a mechanism for transitioning to the long-term solution.  The
   interim solution is based on establishing a branch in the e164.arpa
   tree, which resolvers may locate by following the algorithm described
   in Section 4.  The location of the branch is dependent upon country-
   code length, and thus resolvers must determine the position of the
   branch based on the method described in Section 5.  Finally,
   Section 6 provides a way that implementations following the
   procedures of Sections 4 and 5 may be seamlessly redirected to the