ENUM Implementation Issues and Experiences
RFC 5483

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Network Working Group                                          L. Conroy
Request for Comments: 5483                                          RMRL
Category: Informational                                      K. Fujiwara
                                                                    JPRS
                                                              March 2009

               ENUM Implementation Issues and Experiences

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
   and restrictions with respect to this document.

Abstract

   This document captures experiences in implementing systems based on
   the ENUM protocol and experiences of ENUM data that have been created
   by others.  As such, it clarifies the ENUM and Dynamic Delegation
   Discovery System standards.  Its aim is to help others by reporting
   both what is "out there" and potential pitfalls in interpreting the
   set of documents that specify the ENUM protocol.  It does not revise
   the standards but is intended to provide technical input to future
   revisions of those documents.

Conroy & Fujiwara            Informational                      [Page 1]
RFC 5483                    ENUM Experiences                  March 2009

Table of Contents

   1. Introduction ....................................................3
      1.1. Document Goal ..............................................3
      1.2. Terminology ................................................3
   2. Character Sets and ENUM .........................................4
      2.1. Character Sets - Non-ASCII Considered Harmful ..............4
           2.1.1. Non-ASCII in the Regular Expression Field ...........5
           2.1.2. Non-ASCII Support - Conclusions .....................6
      2.2. Case Sensitivity ...........................................7
      2.3. Regexp Field Delimiter .....................................7
      2.4. Regexp Meta-Character Issue ................................8
   3. Unsupported NAPTRs ..............................................8
      3.1. Non-Compliant Client Behaviour .............................9
   4. ENUM NAPTR Processing ..........................................10
      4.1. Common Non-Compliant Client Behaviour .....................11
           4.1.1. Example ............................................11
      4.2. Order/Priority Values - Processing Sequence ...............12
      4.3. Use of Order and Preference Fields ........................13
      4.4. NAPTRs with Identical ORDER/PRIORITY Values ...............14
           4.4.1. Compound NAPTRs and Implicit
                  ORDER/REFERENCE Values .............................14
      4.5. Processing Order Value across Domains .....................15
   5. Non-Terminal NAPTR Processing ..................................16
      5.1. Non-Terminal NAPTRs - Necessity ...........................16
      5.2. Non-Terminal NAPTRs - Considerations ......................17
           5.2.1. Non-Terminal NAPTRs - General ......................17
           5.2.2. Non-Terminal NAPTRs - Loop Detection and Response ..17
           5.2.3. Field Content in Non-Terminal NAPTRs ...............17
   6. Backwards Compatibility ........................................20
      6.1. Services Field Syntax .....................................20
   7. Collected Implications for ENUM Provisioning ...................21
   8. Collected Implications for ENUM Clients ........................23
      8.1. Non-Terminal NAPTR Processing .............................25
   9. Security Considerations ........................................26
   10. Acknowledgements ..............................................27
   11. References ....................................................27
      11.1. Normative References .....................................27
      11.2. Informative References ...................................29

Conroy & Fujiwara            Informational                      [Page 2]
RFC 5483                    ENUM Experiences                  March 2009

1.  Introduction

1.1.  Document Goal

   The goal of this document is to clarify the ENUM and Dynamic
   Delegation Discovery System (DDDS) standards.  It does not itself
   revise ENUM or DDDS standards but is intended to provide technical
   input to future revisions of those documents.  It also serves to
   advise implementers on the pitfalls that they may find.  It