ENUM WG                                                      J. Peterson
Internet-Draft                                                   NeuStar
Expires: August 25, 2003                               February 24, 2003

             Enumservice Registration for Presence Services

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   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 (2003).  All Rights Reserved.


   This document registers an ENUM service for presence services (as
   described in RFC2778 [3]) pursuant to the guidelines in RFC2916bis
   [2].  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 . . . . . . . . . . . . . . . . . . . 4
   4. The 'E2U+pres' enumservice . . . . . . . . . . . . . . . . . . . 4
   5. Example of E2U+pres enumservice  . . . . . . . . . . . . . . . . 5
   6. Security Considerations  . . . . . . . . . . . . . . . . . . . . 5
   7. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . . 6
      Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
      References . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   A. To Do  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
      Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 8

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1. Introduction

   ENUM (E.164 Number Mapping, RFC2916 [1]) is a system that uses DNS
   (Domain Name Service, RFC1034 [9]) to translate telephone numbers,
   like '+12025332600', into URIs (Uniform Resource Identifiers, RFC2396
   [10]), 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 route transactions.  ENUM is
   currently under revision in RFC2916bis [2]; this document applies to
   the revised version of ENUM described in the work-in-progress.

   Presence is a service defined in RFC2778 [3] 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 IMPP WG of the IETF has a defined a generic URI used to identify
   a presence service for a particular resource: the 'pres' URI scheme
   (defined in CPP [5]).  This document describes an enumservice for
   advertising presence information associated with an E.164 number.

2. ENUM Service Registration

   As defined in [2], 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

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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-
   telephony communications services advertised by ENUM.

   Endpoints that participate in a presence architecture are known
   (following the framework in RFC2778 [3]) 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 IMPP WG has defined a Presence Information Data
   Format (or PIDF [7]) 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
   [3]); 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
   [14]) 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 will be the 'pres' URI

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   scheme.  There are, however, other URI schemes that can be used to
   identify presence services.  The purpose of a pres URI is to provide
   a generic way of locating a presence service.  Techniques for
   dereferencing the pres URI scheme to locate a presence service are
   given in [6].

   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 [6] details a way to
   discover whether or not the presence protocol(s) supported by the
   watcher is/are also supported by the presentity.  SIP [8] 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).
   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 [4]) 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
   requirements by the work in the IETF IMPP WG.

   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

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   than the existing PSTN, despite the public availability of ENUM

7. IANA Considerations

   This document registers the 'E2U+pres' enumservice under the
   enumservice registry described in the IANA considerations in
   RFC2916bis.  Details of the registration are given in Section 2.


   [1]   Faltstrom, P., "E.164 number and DNS", RFC 2916, September

   [2]   Faltstrom, P. and M. Mealling, "The E.164 to URI DDDS
         Application", draft-ietf-enum-rfc2916bis-03 (work in progress),
         January 2003.

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

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

   [5]   Crocker, D. and J. Peterson, "A Model for Presence and Instant
         Messaging", draft-ietf-impp-pres-02 (work in progress),
         February 2003.

   [6]   Crocker, D. and J. Peterson, "Address Resolution for Instant
         Messaging and Presence", draft-ietf-impp-srv-02 (work in
         progress), February 2003.

   [7]   Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W. and
         J. Peterson, "CPIM Presence Information Data Format", draft-
         ietf-impp-cpim-pidf-07 (work in progress), August 2001.

   [8]   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.

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

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

   [11]  International Telecommunications Union, "Recommendation E.164:

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         The international public telecommunication numbering plan", May
         1997, <http://www.itu.int>.

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

   [13]  Mealling, M. and R. Daniel, "The Naming Authority Pointer
         (NAPTR) DNS Resource Record", RFC 2915, September 2000.

   [14]  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/

Appendix A. To Do

      This document cannot proceed until RFC2916bis has passed.

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