[Search] [txt|pdf|bibtex] [Tracker] [Email] [Nits]

Versions: 00                                                            
Internet Draft                                               R. Stastny
IETF IPTEL WG                                                     OeFEG
                                                             R. Shockey
                                                                Neustar
                                                              L. Conroy
                                            Siemens Roke Manor Research
Document:draft-stastny-iptel-tel-enumdi-00.txt
Expires: March 2005                                        October 2004



               New parameter for the "tel" URI to support ENUM
                    <draft-stastny-iptel-tel-enumdi-00.txt>

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.

  Internet-Drafts are working documents of the Internet Engineering
  Task Force (IETF), its areas, and its working groups. Note that other
  groups may also distribute working documents as Internet-Drafts.

  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time.  It is inappropriate to use Internet-Drafts as reference
  material or to cite them other than a "work in progress."

  The list of current Internet-Drafts can be accessed at
  http://www.ietf.org/1id-abstracts.html

  The list of Internet-Draft Shadow Directories can be accessed at
  http://www.ietf.org/shadow.html

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.


Abstract

   This document defines a new parameter "enumdi" in the "tel" Uniform
   Resource Identifier (URI) to support the handling of ENUM queries in
   SIP proxies, H.323 gatekeepers and other VoIP network elements. The
   presence of the "enumdi" parameter indicates to the VoIP network
   element receiving an URI containing an E.164 number that an ENUM
   query as defined in RFC3761 has already been performed on the E.164
   number indicated by the previous VoIP network element.

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in
   this document are to be interpreted as described in RFC-2119 [1].


Table of Contents

   1. Introduction
   2. Formal Syntax
   3. Normative Rules
   4. Example
   5. Security considerations
   6. IANA Considerations
   7. Normative References
   8. Informative References
   9. Acknowledgments
   10.Author's Addresses


1. Introduction

   VoIP network elements (including UAs) may be set up in different
   ways to handle E.164 [2] numbers during call setup, depending on
   the capabilities provided. One common approach is to query ENUM as
   defined in RFC3761 [3].

   If the ENUM query leads to a result, the call is set-up accordingly.
   If the ENUM query does not lead finally to a result, another
   database may be queried and/or the call may finally routed to the
   PSTN. In doing so, the call may be routed to another VoIP network
   element. To indicate in signalling to this next VoIP element that
   an ENUM query has already be made, the "enumdi" parameter is used,
   to prevent the next VoIP network element from repeating redundant
   queries.


2. Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) as described in RFC2234 [4].

      enumdi                  = *1(enum-dip-indicator)
      enum-dip-indicator      = ";enumdi"


   The "enum-dip-indicator" can appear in the "tel" URI at most once.


3. Normative Rules

   This section discusses how a VoIP network element handles a received
   "tel" URI that contains the "enumdi" parameter or has accessed ENUM
   in e164.arpa for a given E.164 number and needs to add the parameter
   to a "tel" URI.

3.1 Handling an URI with the "enumdi" parameter

   If a VoIP network element receives a "tel" URI containing the
   "enumdi" parameter, the VoIP network element MUST NOT retrieve the
   related information for this number from ENUM in e164.arpa even if
   it would normally do so.

   If the received "tel" URI is to be passed to the next network
   element, the VoIP network element MUST pass on the received URI
   containing the "enumdi" parameter unchanged.

3.2 Adding the "enumdi" parameter to URIs

   When a VoIP network element accesses ENUM in e164.arpa for a given
   E.164 number and the result of the query is NXDOMAIN, and the
   network element chooses to pass the call to the next network element
   by using a "tel" URI, the "enumdi" parameter MUST be set.

   When a VoIP network element accesses ENUM in e164.arpa for a given
   E.164 number and

   - the result of the query includes a NAPTR RR containing a "tel" URI
     that has the same E.164 number, or

   - the result of the query includes a NAPTR RR containing a "tel" URI
     with the "enumdi" parameter set,

   and that "tel" URI is chosen to be passed to the next network
   element, the VoIP network element MUST pass on the retrieved URI
   with the "enumdi" parameter set.


4. Examples

   A. A VoIP network element "server.provider.net" receives a "tel" URI
   <tel:+441632960038>. The VoIP network element accesses the DNS for
   NAPTR RR in 8.3.0.0.6.9.2.3.6.1.4.4.e164.arpa. and gets the response
   NXDOMAIN. The VoIP network element decides to route the call to the
   PSTN via another VoIP network element "gw.provider.net".

   It therefore signals to the next VoIP network element with
       <tel:+441632960038;enumdi>
   or (using the procedures of RFC3261[5] section 19.1.6)
       <sip:+441632960038;enumdi@gw.provider.net;user=phone>.

   B. A VoIP network element "server.provider.net" receives a "tel" URI
   <tel:+441632960038>. The VoIP network element accesses the DNS for
   NAPTR RR in 8.3.0.0.6.9.2.3.6.1.4.4.e164.arpa. and receives the same
   "tel" URI in reply (i.e. <tel:+4416232960038>).

   The VoIP network element decides to route the call to the PSTN via
   another VoIP network element "gw.provider.net".

   It therefore signals to the next VoIP network element with
       <tel:+441632960038;enumdi>
   or (using the procedures of RFC3261[5] section 19.1.6)
       <sip:+441632960038;enumdi@gw.provider.net;user=phone>.

5. Security considerations

   In addition to those security implications discussed in the revised
   "tel" URI [6], there are new security implications associated with
   the defined parameter.

   If the "enumdi" is illegally inserted into the "tel" URI when the
   signaling message carrying the "tel" URI is en route to the
   destination entity, the call may be routed to the PSTN network,
   incurring unexpected charges or the causing a downstream VoIP
   network element to reject the call setup.

   It is less a problem if the "enumdi" is illegally removed.  An
   additional ENUM query may be performed to retrieve the routing
   number information and have the "enumdi" included again.

   It is RECOMMENDED that protocols carrying the "tel" URI ensure
   message integrity during the message transfer between the two
   communicating network elements so as to detect any unauthorized
   changes to the content of the "tel" URI and other information.

6.  IANA Considerations

   This document requires no IANA actions.

7.  Normative References

   1  Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997

   2  ITU-T Recommendation E.164, "The international public
          telecommunication numbering plan", May 1997.

   3  Faltstrom, P. and Mealling M., "The E.164 to Uniform Resource
      Identifiers (URI) Dynamic Delegation Discovery System (DDDS)
      Application (ENUM)", RFC 3761, April 2004.

   4 D. Crocker and P. Overell, RFC2234, "Augmented BNF for Syntax
          Specifications: ABNF", November 1997.

   5 J. Rosenberg, et al., RFC3261, "SIP: Session Initiation
          Protocol", June 2002.

   6  H. Schulzrinne, draft-ietf-iptel-rfc2806bis-07.txt, "The tel URI
          for Telephone Calls", April 9, 2004. (work in progress)


8.  Informative References

   7  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
      9, RFC 2026, October 1996.

   8  Bradner, S., "Intellectual Property Rights in IETF Technology",
      BCP 79, RFC3668, February 2004

   9  Bradner, S., "IETF Rights in Contributions", BCP 78, RFC3667,
      February 2004

9.  Acknowledgments

   The authors would like to thank James Yu for his comments.


10.  Author's Addresses

   Lawrence Conroy
   Siemens Roke Manor Research
   Roke Manor
   Romsey
   United Kingdom
   Phone: +44-1794-833666
   Email: lwc@roke.co.uk

   Richard Shockey
   Neustar Inc.
   46000 Center Oak Plaza
   Sterling, VA  20166
   Phone: +1.571.434.5651
   Email:richard.shockey@neustar.biz

   Richard Stastny
   OeFEG
   Arsenal Objekt 24, Postbox 147
   1140 Vienna
   Austria
   Phone: +43 664 420 4100
   Email: richard.stastny@oefeg.at


This draft expires in March 2005.

Full Copyright Statement

  Copyright (C) The Internet Society (2004).  This document is subject
  to the rights, licenses and restrictions contained in BCP 78, and
  except as set forth therein, the authors retain all their rights.

Disclaimer of Warranty

  This document and the information contained herein are provided on an
  "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
  OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
  ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
  INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
  INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
  WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Disclaimer of Validity

  The IETF takes no position regarding the validity or scope of any
  Intellectual Property Rights or other rights that might be claimed
  to pertain to the implementation or use of the technology
  described in this document or the extent to which any license
  under such rights might or might not be available; nor does it
  represent that it has made any independent effort to identify any
  such rights.  Information on the procedures with respect to rights
  in RFC documents can be found in BCP 78 and BCP 79.

  Copies of IPR disclosures made to the IETF Secretariat and any
  assurances of licenses to be made available, or the result of an
  attempt made to obtain a general license or permission for the use
  of such proprietary rights by implementers or users of this
  specification can be obtained from the IETF on-line IPR repository
  at http://www.ietf.org/ipr.

  The IETF invites any interested party to bring to its attention
  any copyrights, patents or patent applications, or other
  proprietary rights that may cover technology that may be required
  to implement this standard.  Please address the information to the
  IETF at ietf-ipr@ietf.org.


Acknowledgement

  Funding for the RFC Editor function is currently provided by the
  Internet Society.