ENUM WG                                                      J. Peterson
Internet-Draft                                                   NeuStar
Expires: November 18, 2004                                  May 20, 2004

             Enumservice Registration for Presence Services

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

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


   This document registers an ENUM service for presence.  Specifically,
   this document focuses on provisioning pres URIs in ENUM.

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Table of Contents

   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2. ENUM Service Registration  . . . . . . . . . . . . . . . . . . . 3
   3. Presence for E.164 numbers . . . . . . . . . . . . . . . . . . . 3
   4. The 'E2U+pres' enumservice . . . . . . . . . . . . . . . . . . . 4
   5. Example of E2U+pres enumservice  . . . . . . . . . . . . . . . . 5
   6. Security Considerations  . . . . . . . . . . . . . . . . . . . . 5
   7. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . . 6
   8. IPR Considerations . . . . . . . . . . . . . . . . . . . . . . . 6
      Normative References . . . . . . . . . . . . . . . . . . . . . . 6
      Informative References . . . . . . . . . . . . . . . . . . . . . 7
      Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
      Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 8

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1. Introduction

   ENUM (E.164 Number Mapping, RFC3761 [1]) is a system that uses DNS
   (Domain Name Service, RFC1034 [8]) to translate telephone numbers,
   like '+12025332600', into URIs (Uniform Resource Identifiers, RFC2396
   [9]), like 'pres:user@host.com'.  ENUM exists primarily to facilitate
   the interconnection of systems that rely on telephone numbers with
   those that use URIs to identify resources.

   Presence is a service defined in RFC2778 [2] that allows users of a
   communications service to monitor one another's availability and
   disposition in order to make decisions about communicating.  Presence
   information is highly dynamic, and generally characterizes whether a
   not a user is online or offline, busy or idle, away from
   communications devices or nearby, and the like.

   The IETF has defined a generic URI used to identify a presence
   service for a particular resource: the 'pres' URI scheme (defined in
   CPP [4]).  This document describes an enumservice for advertising
   presence information associated with an E.164 number.

2. ENUM Service Registration

   As defined in [1], the following is a template covering information
   needed for the registration of the enumservice specified in this

      Service Name: "E2U+pres"

      URI Scheme(s): "pres:"

      Functional Specification: see Section 4

      Security considerations: see Section 6

      Intended usage: COMMON

      Author: Jon Peterson (jon.peterson@neustar.biz)

      Any other information that the author deems interesting: See
      Section 3

3. Presence for E.164 numbers

   This document specifies an enumservice field that allows presence
   information to be provided for an E.164 number.  This may include
   presence states associated with telephones, or presence of non-

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   telephony communications services advertised by ENUM.

   Endpoints that participate in a presence architecture are known
   (following the framework in RFC2778 [2]) as watchers and
   presentities.  Watchers subscribe to the presence of presentities,
   and are notified when the presence of a presentity changes.  Watchers
   generally monitor the presence of a group of presentities with whom
   they have an ongoing association.  As an example, consider a way that
   this might apply a telephony service.  Most cellular telephones today
   have an address-book like feature, a small database of names and
   telephone numbers.  Such a telephone might act as a watcher,
   subscribing to the presence of some or all of the telephone numbers
   in its address book.  The display of the telephone might then show
   its user, when a presence-enabled telephone number is selected, the
   availability of the destination.  With this information, user might
   change their calling habits to correspond better to the availability
   of their associates.

   The presence information that is shared varies by communications
   service.  The IETF has defined a Presence Information Data Format (or
   PIDF [6]) for describing the presence data associated with a
   presentity.  The baseline PIDF specification declares only two
   presence states: OPEN and CLOSED (these terms are defined in RFC2778
   [2]); the former suggests that the destination resource is able to
   accept communication requests, the latter that it is not.  These two
   states provide useful but rudimentary insight into the communications
   status of a presentity; for that reason, PIDF is an extensible
   format, and new sorts of status can be defined for specific
   communications services.  For example, a telephony-based presence
   service might define a status corresponding to 'busy'.  Extending
   PIDF for telephony services is however outside the scope of this

4. The 'E2U+pres' enumservice

   Traditionally, the services field of a NAPTR record (as defined in
   [12]) contains a string that is composed of two subfields: a
   'protocol' subfield and a 'resolution service' subfield.  ENUM in
   particular defines an 'E2U' (E.164 to URI) resolution service.  This
   document defines an 'E2U+pres' enumservice for presence.

   The scheme of the URI that will appear in the regexp field of a NAPTR
   record using the 'E2U+pres' enumservice SHOULD be the 'pres' URI
   scheme.  Other URI schemes appropriate to presence services MAY be
   used; however, the use of the 'pres' URI scheme ensures a greater
   level of compatibility than the use of any URI specific to a
   particular presence protocol.  The purpose of a pres URI is to
   provide a generic way of locating a presence service.  Techniques for

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   dereferencing the pres URI scheme to locate a presence service are
   given in [5].

   The 'pres' URI scheme does not identify any particular protocol that
   will be used to handle presence operations (such as subscriptions and
   notifications).  Rather, the mechanism in [5] details a way to
   discover whether or not the presence protocol(s) supported by the
   watcher is/are also supported by the presentity.  SIP [7] is one
   protocol that can be used to convey presence information and manage

5. Example of E2U+pres enumservice

   The following is an example of the use of the enumservice registered
   by this document in a NAPTR resource record.

      IN NAPTR 100 10 "u" "E2U+pres"  "!^.*$!pres:jon.peterson@neustar.biz!"     .

6. Security Considerations

   DNS does not make policy decisions about the records that it shares
   with an inquirer.  All DNS records must be assumed to be available to
   all inquirers at all times.  The information provided within an ENUM
   record set must therefore be considered to be open to the public -
   which is a cause for some privacy considerations.

   However, revealing a pres URI in and of itself is unlikely to
   introduce many privacy concerns, although depending on the structure
   of the URI, it might reveal the full name or employer of the target.
   The use of anonymous URIs mitigates that risk.  There are more
   serious privacy concerns associated with the unauthorized
   distribution of presence information.  For that reason, presence
   protocols have a number of security requirements (detailed in RFC2779
   [3]) that call for authentication of watchers, integrity and
   confidentiality properties, and similar measures to prevent abuse of
   presence information.  Any presence protocol that is used in
   conjunction with the 'pres' URI scheme is required to meet these

   Unlike a traditional telephone number, the resource identified by a
   pres URI may require that callers provide cryptographic credentials
   for authentication and authorization before presence information is
   returned.  In this respect, ENUM in concert with presence protocols
   can actually provide far greater protection from unwanted callers
   than the existing PSTN, despite the public availability of ENUM

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7. IANA Considerations

   This document registers the 'E2U+pres' enumservice under the
   enumservice registry described in the IANA considerations in RFC3761.
   Details of the registration are given in Section 2.

8. IPR Considerations

   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

   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-

Normative References

   [1]  Faltstrom, P. and M. Mealling, "The E.164 to URI DDDS
        Application", RFC 3761, April 2004.

   [2]  Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and
        Instant Messaging", RFC 2778, February 2000.

   [3]  Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
        Presence Protocol Requirements", RFC 2779, February 2000.

   [4]  Peterson, J., "A Model for Presence and Instant Messaging",
        draft-ietf-impp-pres-04 (work in progress), September 2003.

   [5]  Peterson, J., "Address Resolution for Instant Messaging and
        Presence", draft-ietf-impp-srv-04 (work in progress), September

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Informative References

   [6]   Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W. and
         J. Peterson, "CPIM Presence Information Data Format", draft-
         ietf-impp-cpim-pidf-08 (work in progress), May 2003.

   [7]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, May 2002.

   [8]   Mockapetris, P., "Domain Names - Concepts and Facilities", RFC
         1034, November 1987.

   [9]   Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
         Resource Identifiers (URI): Generic Syntax", RFC 2396, August

   [10]  International Telecommunications Union, "Recommendation E.164:
         The international public telecommunication numbering plan", May
         1997, <http://www.itu.int>.

   [11]  Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806, April

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

Author's Address

   Jon Peterson
   NeuStar, Inc.
   1800 Sutter St
   Suite 570
   Concord, CA  94520

   Phone: +1 925/363-8720
   EMail: jon.peterson@neustar.biz
   URI:   http://www.neustar.biz/

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Full Copyright Statement

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