[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-livingood-shockey-enum-npd) 00 01 02 03 04 05 RFC 4769

ENUM Working Group                                         J. Livingood
Internet-Draft                             Comcast Cable Communications
Expires: February 7, 2007                                    R. Shockey
                                                                NeuStar
                                                            August 2006


                   IANA Registration for an Enumservice
                   Containing PSTN Signaling Information
                          draft-ietf-enum-pstn-05


Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   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 as "work in progress."

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

   This Internet-Draft will expire on February 4, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).


Abstract

   This document registers the Enumservice type "pstn" and subtype "tel"
   using the URI scheme 'tel', as well as the subtype " sip" using the
   URI scheme 'sip' as per the IANA registration process defined in the
   ENUM specification, RFC 3761.  This Enumservice is used to facilitate
   the routing of telephone calls in those countries where Number
   Portability exists.



Livingood & Shockey    Expires February 4, 2007               [Page 1]

Internet-Draft             PSTN Enumservice                August 2006



Table of Contents

   1. Terminology....................................................2
   2. Introduction...................................................2
   3. Distribution of Data...........................................4
   4. ENUM Service Registration for PSTN.............................4
      4.1 ENUM Service Registration for PSTN with Subtype "tel"......4
      4.2 ENUM Service Registration for PSTN with Subtype "sip"......5
   5. Examples.......................................................6
      5.1 Example of a Ported Number, Using a 'tel' URI Scheme.......6
      5.2 Example of a Ported Number, Using a 'sip' URI Scheme.......6
      5.3 Example of a Non-Ported Number, Using a 'tel' URI Scheme...6
      5.4 Example of a Non-Ported Number, Using a 'sip' URI Scheme...6
      5.5 Example Using a Regular Expression.........................7
   6. Implementation Recommendations.................................7
      6.1 Call Processing When Multiple Records Are Returned.........7
      6.2 NAPTR Configuration issues.................................7
   7. Example of E2U+pstn in Call Processing.........................8
      7.1 Dialed Number Not Available On-Net.........................8
      7.2 Dialed Number Available On-Net and on the PSTN.............8
   8. Security Considerations........................................8
   9. IANA Considerations............................................9
   10. Acknowledgements..............................................9
   11. References...................................................10
      11.1 Normative References.....................................10
      11.2 Informative References...................................10
   Authors' Addresses...............................................11
   Intellectual Property and Copyright Statements...................11


1. Terminology

   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 BCP 14, RFC-2119 [1].


2. Introduction

   ENUM (E.164 Number Mapping, RFC 3761 [1]) is a technology that
   transforms E.164 numbers (The International Public Telecommunication
   Numbering Plan, ITU-T Recommendation E.164 [2]) into domain names and
   then uses DNS (Domain Name System, RFC 1034 [3]) delegation through
   NS records and NAPTR records (Dynamic Delegation Discovery System
   (DDDS) Part Three: The Domain Name System (DNS) Database, RFC 3403
   [4]) to look up what services are available for a specific domain
   name.



Livingood & Shockey    Expires February 4, 2007               [Page 2]

Internet-Draft             PSTN Enumservice                August 2006



   This document registers Enumservices according to the guidelines
   given in RFC 3761 [1] to be used for provisioning in the services
   field of a NAPTR [4] resource record to indicate the types of
   functionality associated with an end point and/or telephone number.
   The registration is defined within the DDDS (Dynamic Delegation
   Discovery System [4][5][6][7][8]) hierarchy, for use with the "E2U"
   DDDS Application defined in RFC 3761.

   Number Portability allows telephone subscribers to keep their
   telephone numbers when they change service provider, move to a new
   location, or change the subscribed services [15].  In many countries,
   such as the United States and Canada, the functions of naming and
   addressing on the Public Switched Telephone Network (PSTN) have been
   abstracted.  In the case of a ported number, the dialed number is not
   directly routable on the PSTN and must be translated into a routing
   number for call completion.  Other numbers, which are not ported, and
   which can be routed directly on the PSTN based on the dialed number,
   are typically assigned to carriers and other entities in large blocks
   or pools.  Number Portability and other numbering information is
   distributed in a variety of methods and formats around the world.

   The Enumservices described here could enable service providers to
   place ported, pooled, and blocks of numbers and their associated PSTN
   contact information, into externally available or highly locally
   cached ENUM databases.  This, in turn, could enable such parties to
   consolidate all telephone number lookups in their networks into a
   single ENUM lookup, thereby simplifying call routing and network
   operations, which would then result in either an on-net, or IP-based
   response, or off-net, PSTN-based response.

   The following Enumservice is registered with this document: "pstn" to
   indicate PSTN routing data, including number portability data, non-
   ported telephone number data (individually or in number blocks), and
   other PSTN-oriented data that is associated with E.164 telephone
   numbers.  The purpose of this Enumservice is to provide routing
   information for telephone numbers which do not designate an endpoint
   resident on the public Internet or a private/peered Internet Protocol
   (IP) network.  Thus, these are numbers which are only routable via
   the traditional PSTN, even if the call originates from an IP network.
   The URIs returned in this service may use the TEL URI parameters
   defined in draft-ietf-iptel-tel-np-10 [10], and implementations must
   be prepared to accept them.

   The service parameters defined in RFC 3761 indicate that a "type" and
   a "subtype" may be specified.  Within this set of specifications, the
   convention is assumed that the "type" (being the more generic term)
   defines the service and the "subtype" defines the URI scheme.



Livingood & Shockey    Expires February 4, 2007               [Page 3]

Internet-Draft             PSTN Enumservice                August 2006


   When only one URI scheme is associated with a given service, it
   should be assumed that an additional URI scheme to be used with this
   service may be added at a later time.  Thus, the subtype is needed to
   identify the specific Enumservice intended.


3. Distribution of Data

   The distribution of number portability data is often highly
   restricted either by contract or regulation of a National Regulatory
   Authority (NRA), therefore NAPTR records specified herein may or may
   not be part of the e164.arpa DNS tree.

   The authors believe that it is more likely that these records will be
   distributed on a purely private basis.  Distribution of this NAPTR
   data could be either (a) on a private basis (within a service
   provider's internal network, or on a private basis between one or
   more parties using a variety of security mechanisms to prohibit
   general public access), (b) openly available or, (c) distributed by
   the relevant number portability organization or other industry
   organization, but possibly on a national basis and subject to or in
   accordance with national regulatory policy.

   If such data was distributed nationally, the national telephone
   numbering authority, or some other regulatory body or numbering
   organization, may have jurisdiction.  Such a body may choose to
   restrict distribution of the data in such a way that it may not pass
   over that country's national borders.

4. ENUM Service Registration for PSTN

4.1 ENUM Service Registration for PSTN with Subtype "tel"

   Enumservice Name: "pstn"

   Enumservice Type: "pstn"

   Enumservice Subtype: "tel"

   URI Schemes: 'tel:'

   Functional Specification:

   These Enumservices indicate that the remote resource identified can
   be addressed by the associated URI scheme in order to initiate a
   telecommunication session, which may include two-way voice or other
   communications, to the PSTN.  These URIs may contain number
   portability data as specified in draft-ietf-iptel-tel-np-10 [10].



Livingood & Shockey    Expires February 4, 2007               [Page 4]

Internet-Draft             PSTN Enumservice                August 2006


   Security Considerations: See Section 9.

   Intended Usage: COMMON

   Authors:

   Jason Livingood (jason_livingood@cable.comcast.com)
   Richard Shockey (richard.shockey@neustar.biz)

   Any other information the author deems interesting:

   A Number Portability Dip Indicator (npdi) should be used in practice
   (see examples below in Section 5).

4.2 ENUM Service Registration for PSTN with Subtype "sip"

   Enumservice Name: "pstn"

   Enumservice Type: "pstn"

   Enumservice Subtypes: "sip"

   URI Schemes: 'sip:'

   Functional Specification:

   These Enumservices indicate that the remote resource identified can
   be addressed by the associated URI scheme in order to initiate a
   telecommunication session, which may include two-way voice or other
   communications, to the PSTN.

   Security Considerations: See Section 9.

   Intended Usage: COMMON

   Authors:

   Jason Livingood (jason_livingood@cable.comcast.com)
   Richard Shockey (richard.shockey@neustar.biz)

   Any other information the author deems interesting:

   A Number Portability Dip Indicator (npdi) should be used in practice
   (see examples below in Section 5).







Livingood & Shockey    Expires February 4, 2007               [Page 5]
Internet-Draft             PSTN Enumservice                August 2006


5. Examples

   The following sub-sections document several examples for illustrative
   purposes.  These examples shall in no way limit the various forms
   that this Enumservice may take.

5.1 Example of a Ported Number, Using a 'tel' URI Scheme

   $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      NAPTR 10 100 "u" "E2U+pstn:tel"
      "!^.*$!tel:+1-215-555-0123;npdi;rn=+1-215-555-0199!".

   In this example, a Routing Number (rn) and a Number Portability Dip
   Indicator (npdi) are used as shown in draft-ietf-iptel-tel-np-10
   [10].  The 'npdi' field is included in order to prevent subsequent
   lookups in legacy-style PSTN databases.

5.2 Example of a Ported Number, Using a 'sip' URI Scheme

   $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      NAPTR 10 100 "u" "E2U+pstn:sip"
      "!^.*$!sip:+1-215-555-0123;npdi;rn=+1-215-555-0199
   @gw.example.com;user=phone!".

   In this example, a Routing Number (rn) and a Number Portability Dip
   Indicator (npdi) are used as shown in draft-ietf-iptel-tel-np-10
   [10].  The 'npdi' field is included in order to prevent subsequent
   lookups in legacy-style PSTN databases.  The method of conversion
   from a tel to a SIP URI is as demonstrated in RFC 3261, Section 
   19.1.6 [11], as well as in , draft-ietf-iptel-tel-np-10 Section 6
   [10].

5.3 Example of a Non-Ported Number, Using a 'tel' URI Scheme

   $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      NAPTR 10 100 "u" "E2U+pstn:tel"
      "!^.*$!tel:+1-215-555-0123;npdi!".

   In this example, a Number Portability Dip Indicator (npdi) is used
   [10].  The 'npdi' field is included in order to prevent subsequent
   lookups in legacy-style PSTN databases.

5.4 Example of a Non-Ported Number, Using a 'sip' URI Scheme

   $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      NAPTR 10 100 "u" "E2U+pstn:sip"
      "!^.*$!sip:+1-215-555-0123;npdi@gw.example.com;user=phone!".





Livingood & Shockey    Expires February 4, 2007               [Page 6]

Internet-Draft             PSTN Enumservice                August 2006


   In this example, a Number Portability Dip Indicator (npdi) is used
   [10].  The 'npdi' field is included in order to prevent subsequent
   lookups in legacy-style PSTN databases.  The method of conversion
   from a tel to a SIP URI is as demonstrated in RFC 3261, Section 
   19.1.6 [11], as well as in , draft-ietf-iptel-tel-np-10 Section 6
   [10].

5.5 Example Using a Regular Expression

   $ORIGIN 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      NAPTR 10 100 "u" "E2U+pstn:tel"
      "!(^.*)$!tel:\1;npdi!".

   In this example, a regular expression replacement function is used to
   reduce the size of the NAPTR record.  The tel URI uses "\1" which
   would dynamically replace the expression with the TN plus the leading
   "+", in this case +1-215-555-0123.


6. Implementation Recommendations

6.1 Call Processing When Multiple Records Are Returned

   It is likely that that both E2U+sip and E2U+pstn Enumservice type
   records will be returned for a given query.  In this case, this could
   result in what is essentially an on-net and off-net pstn record.
   Thus, one record gives the associated address on an IP network, while
   the other gives the associated address on the PSTN.  As with multiple
   records resulting from a typical ENUM query of the e164.arpa tree, it
   is up to the application using an ENUM resolver to determine which
   record(s) to use and which record(s) to ignore.  Implementers should
   take this into consideration and build logic into their applications
   that can select appropriately from multiple records based on
   business, network, or other rules.  For example, such a resolver
   could be configured to grant preference to the on-net record, or
   execute other logic as required by the application.

6.2 NAPTR Configuration issues

   It has been suggested that tel URIs may be easier and more efficient
   to use in practice than SIP URIs.  In addition, the use of tel URIs
   may result in somewhat smaller NAPTR records which, when considering
   adding hundreds of millions of these records to the DNS, could have a
   substantial impact on the processing and storage requirements for
   service providers or other entities making use of this Enumservice
   type.

   Implementers may wish to consider using regular expressions in order
   to reduce the size of individual NAPTRs.  This will have a


Livingood & Shockey    Expires February 4, 2007               [Page 7]

Internet-Draft             PSTN Enumservice                August 2006


   significant effect on the overall size of the database involved.
   Using the Section 5.5 example from above, this is 11 bytes per
   record.


7. Example of E2U+pstn in Call Processing

   This is an example of how a switch, proxy, or other calling
   application may make use of this Enumservice type during the call
   initiation process.

7.1 Dialed Number Not Available On-Net
      a) A user, which is connected to a calling application, dials an
         E.164 telephone number: +1-215-555-0123.
      b) The calling application uses the dialed number to form a NAPTR
         record: 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      c) The DNS finds an E2U+pstn:tel record and returns a tel URI for
         processing by the calling application: tel:+1-215-555-
         0123;npdi.
      d) The calling application uses routing logic to determine which
         media gateway is the closest to this number and routes the
         call appropriately.

7.2 Dialed Number Available On-Net and on the PSTN
      a) A user, which is connected to a calling application, dials an
         E.164 telephone number: 1-215-555-0123.
      b) The calling application uses the dialed number to form a NAPTR
         record: 3.2.1.0.5.5.5.5.1.2.1.e164.arpa.
      c) The DNS finds both an E2U+pstn record, as well as an E2U+sip
         record, since this number happens to be on the IP network of a
         connected network.
      d) The calling application prioritizes the on-net record first:
         sip:+1-215-555-0123;npdi@gw.example.com;user=phone.
      e) The calling application sets up the SIP call to
         gw.example.com.
      f) Should the IP call route fail for whatever reason, the calling
         application may be able to utilize the E2U+pstn record to
         invoke a fallback route to a media gateway that is connected
         to the PSTN.


8. Security Considerations

   DNS, as used by ENUM, is a global, distributed database.  Should
   implementers of this specification use e164.arpa or any other
   publicly available domain as the tree for maintaining PSTN
   Enumservice data, this information would be visible to anyone
   anonymously.  While this is not qualitatively different from
   publication in a Telephone Directory, it does open or ease access to


Livingood & Shockey    Expires February 4, 2007               [Page 8]

Internet-Draft             PSTN Enumservice                August 2006


   such data without any indication that such data has been accessed or
   by whom it has been accessed.

   Such data harvesting by third parties is often used to generate lists
   of targets for unsolicited information.  Thus, a third party could
   use this to generate a list that they can use to make unsolicited
   "telemarketing" phone calls.  Many countries have do-not-call
   registries or other legal or regulatory mechanisms in place to deal
   with such abuses.

   As noted earlier Carriers, service providers, and other users may
   simply choose not to publish such information in the public e164.arpa
   tree, but may instead simply publish this in their internal ENUM
   routing database that is only able to be queried by trusted elements
   of their network, such as softswitches and SIP proxy servers.  They
   may also choose to publish such information in a carrier-only branch
   of the E164.ARPA tree, should one be created.

   Although an E.164 telephone number does not appear to reveal as much
   identity information about a user as a name in the format
   sip:username@hostname or email:username@hostname, the information is
   still publicly available, thus there is still the risk of unwanted
   communication.

   An analysis of threats specific to the dependence of ENUM on the DNS
   and the applicability of DNSSEC [13] to this is provided in RFC 3761
   [1].  A thorough analysis of threats to the DNS itself is covered in
   RFC 3833 [14].


9. IANA Considerations

   This document registers the 'pstn' Enumservice type and the subtype
   "tel" and "sip" under the Enumservice registry described in the IANA
   considerations in RFC 3761.  Details of this registration are
   provided in Section 4 of this document.


10. Acknowledgements

   The authors wish to thank Lawrence Conroy, Tom Creighton, Jason
   Gaedtke, Jaime Jimenez, Chris Kennedy, Alexander Mayrhofer, Doug
   Ranalli, Jonathan Rosenberg, Bob Walter, and James Yu for their
   helpful discussions of this topic, and detailed reviews of this
   document.  The authors also wish to thank the IETF's ENUM Working
   Group for helpful feedback in refining and developing this draft.





Livingood & Shockey    Expires February 4, 2007               [Page 9]

Internet-Draft             PSTN Enumservice                August 2006


11. References

11.1 Normative References

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

   [2] ITU-T, "The International Public Telecommunication Number Plan",
   Recommendation E.164, May 1997.

   [3] Mockapetris, P., "DOMAIN NAMES - CONCEPTS AND FACILITIES", RFC
   1034, November 1987.

   [4] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
   Three: The Domain Name System (DNS) Database", RFC 3403, October
   2002.

   [5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
   One: The Comprehensive DDDS", RFC 3401, October 2002.

   [6] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
   Two: The Algorithm", RFC 3402, October 2002.

   [7] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
   Four: The Uniform Resource Identifiers (URI)", RFC 3404, October
   2002.

   [8] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
   Five: URI.ARPA Assignment Procedures", RFC 3405, October 2002.

   [9] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
   December 2004.

   [10] Yu, J., "Number Portability Parameters for the "tel" URI",
   draft-ietf-iptel-tel-np-10, May 2006.

   [11] Rosenberg, J., et al., "SIP: Session Initiation Protocol", RFC
   3261, June 2002.

11.2 Informative References

   [12] Bradner, et al., "IANA Registration for Enumservices email, fax,
   mms, ems and sms", RFC 4355, January 2006.

   [13] Arends, R. and et al., "Protocol Modifications for the DNS
   Security Extensions", RFC 4035, March 2005.




Livingood & Shockey    Expires February 4, 2007              [Page 10]

Internet-Draft             PSTN Enumservice                August 2006


   [14] Atkins, D. and Austein, R., "Threat Analysis of the Domain Name
   System (DNS)", RFC 3833, August 2004.

   [15] Foster, M., McGarry, T., and Yu, J., "Number Portability in the
   GSTN: An Overview", RFC 3482, February 2003.

   [16] Peterson, J., "enumservice Registration for Session Initiation
   Protocol (SIP) Addresses-of-Record", RFC 3764, April 2004.


Authors' Addresses

   Jason Livingood
   Comcast Cable Communications
   1500 Market Street
   Philadelphia, PA 19102
   USA

   Phone: +1-215-981-7813
   Email: jason_livingood@cable.comcast.com


   Richard Shockey
   NeuStar
   46000 Center Oak Plaza
   Sterling, VA 20166
   USA

   Phone: +1-571-434-5651
   Email: richard.shockey@neustar.biz


Intellectual Property and Copyright Statements

   Intellectual Property Statement

   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



Livingood & Shockey    Expires February 4, 2007              [Page 11]

Internet-Draft             PSTN Enumservice                August 2006


   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.


   Disclaimer of Validity

   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.


   Copyright Statement

   Copyright (C) The Internet Society (2006).  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.


   Acknowledgment

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


















Livingood & Shockey    Expires February 4, 2007              [Page 12]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/