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rfc:rfc4415

Network Working Group R. Brandner Request for Comments: 4415 Siemens AG Category: Standards Track L. Conroy

                                           Siemens Roke Manor Research
                                                            R. Stastny
                                                                 Oefeg
                                                         February 2006
              IANA Registration for Enumservice Voice

Status 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 (2006).

Abstract

 This document registers the Enumservice "voice" (which has a defined
 subtype "tel"), as per the IANA registration process defined in the
 ENUM specification RFC 3761.  This service indicates that the contact
 held in the generated Uniform Resource Identifier (URI) can be used
 to initiate an interactive voice (audio) call.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
 3.  Voice Service Registration  . . . . . . . . . . . . . . . . . . 3
 4.  Example of voice:tel Enumservice  . . . . . . . . . . . . . . . 4
 5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
 6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
 7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . 6
     7.2.  Informative References  . . . . . . . . . . . . . . . . . 6

Brandner, et al. Standards Track [Page 1] RFC 4415 IANA Voice Enumservice Registration February 2006

1. Introduction

 ENUM (E.164 Number Mapping, RFC 3761 [1]) is a system that transforms
 E.164 numbers [2] into domain names and then uses DNS (RFC 1034 [3])
 features such as delegation through NS records, and the use of Naming
 Authority Pointer (NAPTR) records, to look up the communication
 services available for a specific domain name.
 This document registers an Enumservice according to the guidelines
 given in RFC 3761 to be used for provisioning in the services field
 of a NAPTR [4] resource record to indicate what class of
 functionality a given endpoint offers.  The registration is defined
 within the Dynamic Delegation Discovery System (DDDS, [5] [6] [4] [7]
 [8]) hierarchy, for use with the "E2U" DDDS application defined in
 RFC 3761.
 Enumservices have a type and subtype.  This latter is optional, as it
 may be implicit in the service type.  The type defines the kind of
 communication session that can be initiated using the contact
 indicated by the URI generated by the enclosing NAPTR.  In
 telecommunications engineering terms, it reflects the "teleservice".
 The subtype defines the subsystem that is to be used to initiate the
 communication session.  Note that the subtype definition is usually
 associated with the URI scheme that is to be used.
 Both the type and subtype (where present) must be supported for the
 NAPTR to be used by a potential correspondent.
 There are a number of DDDS applications in addition to ENUM (for
 example, see [7] and [8]).  However, an Enumservice indication
 operates only within the context of the "E2U" (ENUM) DDDS
 Application.
 Whilst the protocol elements that make up ENUM are defined in the
 above documents and in this one, further examples of the use to which
 these may be put are given in other documents, for example, in ETSI
 TS 102 172 [11].
 This document registers the Enumservice "voice" (which has a defined
 subtype "tel"), as per the IANA registration process defined in the
 ENUM specification RFC 3761.  This service indicates that the contact
 held in the generated URI can be used to initiate an interactive
 voice (audio) call.

Brandner, et al. Standards Track [Page 2] RFC 4415 IANA Voice Enumservice Registration February 2006

2. 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 [9].

3. Voice Service Registration

 Enumservice Name: "voice"
 Enumservice Type: "voice"
 Enumservice Subtype: "tel"
 URI Scheme: 'tel:'
 Functional Specification:
    The kind of communication indicated by this Enumservice is
    "Interactive Voice".  From a protocol perspective, this
    communication is expected to involve bidirectional media streams
    carrying audio data.
    A client may imply that the person controlling population of a
    NAPTR holding this Enumservice indicates his capability to engage
    in an interactive voice session when contacted using the URI
    generated by this NAPTR.
 Security Considerations:
    See Section 5.
 Intended Usage: COMMON
 Authors:
    Rudolf Brandner, Lawrence Conroy, and Richard Stastny (for author
    contact detail, see Authors' Addresses section)
 Any other information the author deems interesting:
    This Enumservice indicates that the person responsible for the
    NAPTR is accessible via the Public Switched Telephone Network
    (PSTN) or Public Land Mobile Network (PLMN) using the value of the
    generated URI.
    The kind of subsystem required to initiate a Voice Enumservice
    with this subtype is a "Dialer".  This is a subsystem that either

Brandner, et al. Standards Track [Page 3] RFC 4415 IANA Voice Enumservice Registration February 2006

    provides a local connection to the PSTN or PLMN or provides an
    indirect connection to those networks.  The subsystem will use the
    telephone number held in the generated URI to place a voice call.
    The voice call is placed to a network that uses E.164 numbers to
    route calls to an appropriate destination.
    Note that the PSTN/PLMN connection may be indirect.  The end user
    receiving this NAPTR may have a relationship with a Communications
    Service Provider that accepts call initiation requests from that
    subsystem using an IP-based protocol such as SIP or H.323, and
    places the call to the PSTN using a remote gateway service.  In
    this case, the provider either may accept requests using "tel:"
    URIs or has a defined mechanism to convert "tel:" URI values into
    a "protocol-native" form.
    The "tel:" URI value SHOULD be fully qualified (using the "global
    phone number" form of RFC 3966 [10]).  A "local phone number" as
    defined in that document SHOULD NOT be used unless the controller
    of the zone in which the NAPTR appears is sure that it can be
    distinguished unambiguously by all clients that can access the
    resource record and that a call from their network access points
    can be routed to that destination.

4. Example of voice:tel Enumservice

 The following is an example of the use of the Enumservice registered
 by this document in a NAPTR resource record.
    $ORIGIN 0.6.9.2.3.6.1.4.4.e164.arpa.
    3.8.0 NAPTR 10 100 "u" "E2U+voice:tel"
       "!^.*$!tel:+441414960000!" .

5. Security Considerations

 DNS, as used by ENUM, is a global, distributed database.  Thus, any
 information stored there is visible to anyone anonymously.  Whilst
 this is not qualitatively different from publication in a telephone
 directory, it does open the data subjects to having "their"
 information collected automatically without any indication that this
 has been done or by whom.
 Such data harvesting by third parties is often used to generate lists
 of targets for unrequested information; in short, they are used to
 address "spam".  Anyone who uses a Web-archived mailing list is aware
 that the volume of "spam" email sent increases when he or she posts
 to the mailing list; publication of a telephone number in ENUM is no
 different, and may be used for attempts to send "junk faxes" or "junk
 SMS", for example.

Brandner, et al. Standards Track [Page 4] RFC 4415 IANA Voice Enumservice Registration February 2006

 Many mailing list users have more than one email address and use
 "sacrificial" email accounts when posting to such lists to help
 filter out unrequested emails sent to them.  This is not so easy with
 published telephone numbers; the PSTN E.164 number assignment process
 is much more involved and usually a single E.164 number (or a fixed
 range of numbers) is associated with each PSTN access.  Thus,
 providing a "sacrificial" phone number in any publication is not
 possible.
 Due to the implications of publishing data on a globally accessible
 database, as a principle the data subjects MUST give their explicit
 informed consent to data being published in ENUM.
 In addition, they should be made aware that, due to storage of such
 data during harvesting by third parties, removal of the data from
 publication will not remove any copies that have been taken; in
 effect, any publication may be permanent.
 However, regulations in many regions will require that the data
 subjects can at any time request that the data be removed from
 publication and that their consent for its publication be explicitly
 confirmed at regular intervals.
 When placing a voice call via the PSTN (or from the Public Land
 Mobile Network), the sender may be charged for this action.  In both
 kinds of networks, calling some numbers is more expensive than
 sending to others; both kinds of networks have "premium rate"
 services that can be charged at a rate considerably more than a
 "normal" call.  As such, it is important that end users be asked to
 confirm placing the call and that the destination number be presented
 to them.  It is the originating user's choice whether or not to place
 a call to this destination number, but the originating user SHOULD be
 shown the destination number so that he or she can make this
 decision.
 In addition to the specific security considerations given above, all
 security considerations given in RFC 3761 apply, as well as the
 DNS-specific threats covered in RFC 3833 [12].

6. IANA Considerations

 The IANA has registered the Enumservice "voice" with a single subtype
 "tel" according to the framework defined in RFC 3761.  The current
 document defines this Enumservice and the expected behaviour of
 clients.

Brandner, et al. Standards Track [Page 5] RFC 4415 IANA Voice Enumservice Registration February 2006

7. References

7.1. 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]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", RFC 2119, BCP 14, March 1997.
 [10]  Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
       December 2004.

7.2. Informative References

 [11]  ETSI, "Minimum Requirements for Interoperability of ENUM
       Implementations", ETSI TS 102 172, January 2005.
 [12]  Atkins, D. and R. Austein, "Threat Analysis of the Domain Name
       System (DNS)", RFC 3833, August 2004.

Brandner, et al. Standards Track [Page 6] RFC 4415 IANA Voice Enumservice Registration February 2006

Authors' Addresses

 Rudolf Brandner
 Siemens AG
 Hofmannstr. 51
 81359 Munich
 Germany
 Phone: +49-89-722-51003
 EMail: rudolf.brandner@siemens.com
 Lawrence Conroy
 Siemens Roke Manor Research
 Roke Manor
 Romsey
 United Kingdom
 Phone: +44-1794-833666
 EMail: lwc@roke.co.uk
 Richard Stastny
 Oefeg
 Postbox 147
 1103 Vienna
 Austria
 Phone: +43-664-420-4100
 EMail: Richard.stastny@oefeg.at

Brandner, et al. Standards Track [Page 7] RFC 4415 IANA Voice Enumservice Registration February 2006

Full 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.
 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.

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 Administrative Support Activity (IASA).

Brandner, et al. Standards Track [Page 8]

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