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Network Working Group                                        J. PetersonRequest for Comments: 3953                                       NeuStarCategory: Standards Track                                   January 2005Telephone Number Mapping (ENUM) ServiceRegistration for Presence ServicesStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2005).Abstract   This document registers a Telephone Number Mapping (ENUM) service for   presence.  Specifically, this document focuses on provisioning pres   URIs in ENUM.Table of Contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .22. ENUM Service Registration  . . . . . . . . . . . . . . . . . . .23. Presence for E.164 Numbers . . . . . . . . . . . . . . . . . . .24. The 'E2U+pres' Enumservice . . . . . . . . . . . . . . . . . . .35. Example of E2U+pres Enumservice  . . . . . . . . . . . . . . . .46. Security Considerations  . . . . . . . . . . . . . . . . . . . .47. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . .58. References . . . . . . . . . . . . . . . . . . . . . . . . . . .58.1.  Normative References . . . . . . . . . . . . . . . . . . .58.2.  Informative References . . . . . . . . . . . . . . . . . .5   Author's Address. . . . . . . . . . . . . . . . . . . . . . . . . .6   Full Copyright Statement. . . . . . . . . . . . . . . . . . . . . .7Peterson                    Standards Track                     [Page 1]

RFC 3953        ENUM Registration for Presence Services     January 20051. Introduction   ENUM (E.164 Number Mapping,RFC 3761 [1]) is a system that uses DNS   (Domain Name Service,RFC 1034 [8]) to translate telephone numbers,   such as +12025332600, into URIs (Uniform Resource Identifiers,RFC2396 [9]), such as 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 inRFC 2778 [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   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   document:      Service name: "E2U+pres"      URI scheme(s): "pres:"      Functional Specification: Seesection 4.      Security considerations: Seesection 6.      Intended usage: COMMON      Author: Jon Peterson (jon.peterson@neustar.biz)      Any other information that the author deems interesting: Seesection 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-   telephony communications services advertised by ENUM.Peterson                    Standards Track                     [Page 2]

RFC 3953        ENUM Registration for Presence Services     January 2005   Endpoints that participate in a presence architecture are known   (following the framework inRFC 2778 [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 how this   might apply to 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, the user   might change their calling habits to correspond better to the   availability of his or her 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 inRFC 2778   [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 statuses 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   document.4.  The 'E2U+pres' Enumservice   Traditionally, the services field of an NAPTR record (as defined in   [10]) contains a string 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 an   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 would the use of any URI specific to a   particular presence protocol.  The purpose of a pres URI is to   provide a generic way to locate a presence service.  Techniques for   dereferencing the pres URI to locate a presence service are given in   [5].Peterson                    Standards Track                     [Page 3]

RFC 3953        ENUM Registration for Presence Services     January 2005   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 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   subscriptions/notifications.5.  Example of E2U+pres enumservice   The following is an example of the use of the enumservice registered   by this document in an NAPTR resource record.$ORIGIN 3.8.0.0.6.9.2.3.6.1.4.4.e164.arpa.   IN NAPTR 100 10 "u" "E2U+pres" "!^.*$!pres:jon.peterson@example.net!"6.  Security Considerations   DNS does not make policy decisions about the records 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 open to the public -- which   is a cause for some privacy considerations.   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 this risk.  More serious privacy concerns   are associated with the unauthorized distribution of presence   information.  For this reason, presence protocols have a number of   security requirements (detailed inRFC 2779 [3]) that call for   authentication of watchers, integrity and confidentiality properties,   and similar measures to prevent abuse of presence information.  Any   presence protocol used in conjunction with the 'pres' URI scheme is   required to meet these requirements.   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 concert with presence protocols, ENUM can actually   provide far greater protection from unwanted callers than does the   existing PSTN, despite the public availability of ENUM records.Peterson                    Standards Track                     [Page 4]

RFC 3953        ENUM Registration for Presence Services     January 20057.  IANA Considerations   This document registers the 'E2U+pres' enumservice under the   enumservice registry described in the IANA considerations inRFC3761.  Details of the registration are given insection 2.8.  References8.1.  Normative References   [1]  Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource        Identifiers (URI) Dynamic Delegation Discovery System (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., Mohr, G., and J. Vincent, "Instant        Messaging / Presence Protocol Requirements",RFC 2779, February        2000.   [4]  Peterson, J., "Common Profile for Presence (CPP)",RFC 3859,        August 2004.   [5]  Peterson, J., "Address Resolution for Instant Messaging and        Presence",RFC 3861, August 2004.8.2.  Informative References   [6]  Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and        J. Peterson, "Presence Information Data Format (PIDF)",RFC3863, August 2004.   [7]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,        Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:        Session Initiation Protocol",RFC 3261, June 2002.   [8]  Mockapetris, P., "Domain Names - Concepts and Facilities", STD        13,RFC 1034, November 1987.   [9]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform        Resource Identifiers (URI): Generic Syntax",RFC 2396, August        1998.   [10] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part        Three: The Domain Name System (DNS) Database",RFC 3403, October        2002.Peterson                    Standards Track                     [Page 5]

RFC 3953        ENUM Registration for Presence Services     January 2005Author's Address   Jon Peterson   NeuStar, Inc.   1800 Sutter St.   Suite 570   Concord, CA  94520   USA   Phone: +1 925/363-8720   EMail: jon.peterson@neustar.biz   URI:http://www.neustar.biz/Peterson                    Standards Track                     [Page 6]

RFC 3953        ENUM Registration for Presence Services     January 2005Full Copyright Statement   Copyright (C) The Internet Society (2005).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   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.Intellectual Property   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 IETF's procedures with respect to rights in IETF Documents can   be found inBCP 78 andBCP 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 athttp://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.Peterson                    Standards Track                     [Page 7]