The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application for Infrastructure ENUM
RFC 5526

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Network Working Group                                       J. Livingood
Request for Comments: 5526                  Comcast Cable Communications
Category: Informational                                        P. Pfautz
                                                                    AT&T
                                                              R. Stastny
                                                            Unaffiliated
                                                              April 2009

            The E.164 to Uniform Resource Identifiers (URI)
        Dynamic Delegation Discovery System (DDDS) Application
                        for Infrastructure ENUM

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.

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Livingood, et al.            Informational                      [Page 1]
RFC 5526                  Infrastructure ENUM                 April 2009

Abstract

   This document defines the use case for Infrastructure ENUM and
   proposes its implementation as a parallel namespace to "e164.arpa",
   as defined in RFC 3761, as the long-term solution to the problem of
   allowing carriers to provision DNS records for telephone numbers
   independently of those provisioned by end users (number assignees).

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Zone Apex for Infrastructure ENUM ...............................3
   4. IANA Considerations .............................................3
   5. Security and Privacy Considerations .............................4
   6. Acknowledgements ................................................4
   7. Normative References ............................................4

1.  Introduction

   ENUM (E.164 Number Mapping [1]) is a system that transforms E.164
   numbers [2] into domain names and then uses the DNS (Domain Name
   Service) [3] to discover NAPTR records that specify what services are
   available for a specific domain name.

   ENUM as originally defined was based on the end-user opt-in
   principle.  While this has great potential to foster new services and
   end-user choices in the long term, the current requirements for
   IP-based interconnection of Voice over IP (VoIP) domains require the
   provisioning of large numbers of allocated or served (hosted) numbers
   of a participating service provider, without the need for individual
   users to opt-in.  This way, service providers can provision their own
   ENUM information that is separate, distinct, and likely to be
   different from what an end-user may provision.  This is particularly
   important if Infrastructure ENUM is used for number-portability
   applications, for example, which an end-user would be unlikely
   interested in provisioning but which a service provider would likely
   find essential.

   In addition, while it is possible that service providers could
   mandate that their users opt-into e164.arpa through end-user contract
   terms and conditions, there are substantial downsides to such an
   approach.  Thus, for all these reasons and many others, ENUM for
   end-user provisioning is ill-suited for use by service providers for
   the interconnection of VoIP domains.

Livingood, et al.            Informational                      [Page 2]
RFC 5526                  Infrastructure ENUM                 April 2009

   As VoIP evolves and becomes pervasive, E.164-addressed telephone
   calls need not necessarily traverse the Public Switched Telephone
   Network (PSTN).  Therefore, VoIP service providers have an interest
   in using ENUM on a so-called "Infrastructure" basis in order to keep