The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application (ENUM)
RFC 6116

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Internet Engineering Task Force (IETF)                        S. Bradner
Request for Comments: 6116                            Harvard University
Obsoletes: 3761                                                L. Conroy
Category: Standards Track                            Roke Manor Research
ISSN: 2070-1721                                              K. Fujiwara
                                                                    JPRS
                                                              March 2011

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

Abstract

   This document discusses the use of the Domain Name System (DNS) for
   storage of data associated with E.164 numbers, and for resolving
   those numbers into URIs that can be used (for example) in telephony
   call setup.  This document also describes how the DNS can be used to
   identify the services associated with an E.164 number.  This document
   obsoletes RFC 3761.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6116.

Copyright Notice

   Copyright (c) 2011 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of

Bradner, Conroy & Fujiwara   Standards Track                    [Page 1]
RFC 6116               ENUM Protocol Specification            March 2011

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
      1.1. Terminology ................................................3
   2. Use of These Mechanisms for Private Dialing Plans ...............4
   3. The ENUM Application Specifications .............................4
      3.1. Application Unique String ..................................4
      3.2. First Well Known Rule ......................................5
      3.3. Expected Output ............................................5
      3.4. Valid Databases ............................................5
           3.4.1. Optional Name Server Additional Section Processing ..6
           3.4.2. Flags ...............................................6
           3.4.3. Service Parameters ..................................7
                  3.4.3.1. ENUM Services ..............................7
                  3.4.3.2. Compound NAPTRs and Implicit
                           ORDER/PREFERENCE Values ....................8
      3.5. The ENUM Algorithm Always Returns a Single Rule ............8
      3.6. Case Sensitivity in ENUM ...................................8
      3.7. Collision Avoidance ........................................9
   4. ENUM Service Example ...........................................10
   5. Clarification of DDDS Use in ENUM ..............................10
      5.1. Collected Implications for ENUM Provisioning ..............11
      5.2. Collected Implications for ENUM Clients ...................13
           5.2.1. Non-Terminal NAPTR Processing ......................15
   6. IANA Considerations ............................................16
   7. Security Considerations ........................................17
      7.1. DNS Security ..............................................17
      7.2. Caching Security ..........................................18
      7.3. Call Routing Security .....................................19
      7.4. URI Resolution Security ...................................19
   8. Acknowledgements ...............................................19
   9. Changes from RFC 3761 ..........................................19
   10. References ....................................................20
      10.1. Normative References .....................................20
      10.2. Informative References ...................................21

Bradner, Conroy & Fujiwara   Standards Track                    [Page 2]
RFC 6116               ENUM Protocol Specification            March 2011