Enumservice Registration for 'acct' URI
RFC 7566

Independent Submission                                           L. Goix
Request for Comments: 7566                   Econocom-Osiatis Ingenierie
Category: Experimental                                             K. Li
ISSN: 2070-1721                                               Individual
                                                               June 2015

                Enumservice Registration for 'acct' URI

Abstract

   This document registers an E.164 Number Mapping (ENUM) service for
   'acct' URIs (Uniform Resource Identifiers).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This is a contribution to the RFC Series, independently
   of any other RFC stream.  The RFC Editor has chosen to publish this
   document at its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7566.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

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Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................2
   3. Use Cases .......................................................2
      3.1. Reverse Phone Lookup .......................................2
      3.2. Routing of Mobile Social Communications ....................3
   4. IANA Registration ...............................................4
   5. Examples ........................................................5
   6. DNS Considerations ..............................................5
   7. Security Considerations .........................................6
   8. IANA Considerations .............................................7
   9. References ......................................................7
      9.1. Normative References .......................................7
      9.2. Informative References .....................................8
   Acknowledgements ...................................................8
   Authors' Addresses .................................................8

1.  Introduction

   ENUM (E.164 Number Mapping, [RFC6116]) is a system that uses DNS
   (Domain Name Service, [RFC1034]) to translate telephone numbers, such
   as '+44 1632 960123', into URIs (Uniform Resource Identifiers,
   [RFC3986]), such as 'acct:user@example.com'.  ENUM exists primarily
   to facilitate the interconnection of systems that rely on telephone
   numbers with those that use URIs to identify resources.

   [RFC7565] defines the 'acct' URI scheme as a way to identify a user's
   account at a service provider.

   This document registers an Enumservice for advertising 'acct' URI
   information associated with an E.164 number.

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 [RFC2119].

3.  Use Cases

3.1.  Reverse Phone Lookup

   In this example, an address book application could issue ENUM queries
   looking for 'acct' URIs corresponding to phone numbers.  This could
   be used to display the account identifier as well as an icon based on
   the host (domain) portion of that URI.

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   Similarly, an endpoint could trigger this resolution process during
   inbound and/or outbound calls to discover an account associated with
   the remote party.

   In general, the provision of an ENUM record to map a phone number
   into an account may be useful for businesses or professional workers
   to identify themselves publicly (in a way similar to vCard ENUM
   records).

3.2.  Routing of Mobile Social Communications

   The Open Mobile Alliance (OMA) develops mobile service enabler
   specifications, which support the creation of interoperable
   end-to-end mobile services independent of the underlying wireless
   platforms, such as GSM (Global System for Mobile communications),
   UMTS (Universal Mobile Telecommunications System), and LTE (Long Term
   Evolution) mobile networks.  The OMA Social Network Web (SNeW)
   Enabler Release [OMA-SNeW] has introduced a number of social
   networking functionalities for mobile subscribers identified by their
   MSISDN (Mobile Subscriber Integrated Services Digital Network number,
   a number uniquely identifying a subscription in a mobile network),
   amongst which is the ability to follow each other's social activities
   across service providers.

   Such functionality requires the global resolution of the MSISDN to
   the corresponding account and provider, in a way analogous to
   Multimedia Messaging Service (MMS) routing, to identify the target
   endpoint for the related messages.  Although alternative solutions
   exist (e.g., based on mobile network operations and/or proprietary
   lookup techniques), ENUM provides a globally accessible mechanism for
   enabling resolution from network entities on behalf of an endpoint,
   or from an endpoint itself.

   For example, a user of a service provider could request to follow the
   social activities of user '+44 1632 960123'.  The home SNeW Server of
   the former user could perform an ENUM query to identify the 'acct'
   URI corresponding to that phone number.  Based on the resulting URI,
   the server could then identify the SNeW Server of the target user and
   route the original user's request to the appropriate endpoint.

   A similar mechanism can apply to other types of social networking-
   related messages or other communications targeted to a mobile
   subscriber.

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4.  IANA Registration

   As defined in [RFC6117], the following is a template covering
   information needed for the registration of the Enumservice specified
   in this document:

           <record>
             <class>Application-Based, Ancillary</class>
             <type>acct</type>
             <urischeme>acct</urischeme>
             <functionalspec>
               <paragraph>
                 This Enumservice indicates that the resource
                 can be identified by the associated 'acct' URI
                 <xref target='RFC7565'/>.
               </paragraph>
             </functionalspec>
             <security>
               For DNS considerations in avoiding loops when
               searching for "acct" NAPTRs, see
               <xref type="rfc" data="7566"/>, Section 6.
               For security considerations, see
               <xref type="rfc" data="7566"/>, Section 7.
             </security>
             <usage>COMMON</usage>
             <registrationdocs>
               <xref type="rfc" data="7566"/>
             </registrationdocs>
             <requesters>
               <xref type="person" data="Laurent_Walter_Goix"/>
             </requesters>
           </record>

           <people>
             <person id="Laurent_Walter_Goix">
               <name>Laurent-Walter Goix</name>
               <org>Econocom-Osiatis Ingenierie</org>
               <uri>mailto:laurent.goix@econocom-osiatis.com</uri>
               <updated>2014-06-18</updated>
             </person>
           </people>

   Note that the registry maintained by IANA is definitive.  For the
   most recent version of the registration, please see the online
   registry <http://www.iana.org/assignments/enum-services>.

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5.  Examples

   The following is an example of the use of the Enumservice registered
   by this document in a Naming Authority Pointer (NAPTR) resource
   record for phone number +44 1632 960123.

   $ORIGIN 3.2.1.0.6.9.2.3.6.1.4.4.e164.arpa.

   IN NAPTR 10 100 "u" "E2U+acct" "!^.*$!acct:441632960123@foo.com!" .

   IN NAPTR 10 101 "u" "E2U+acct" "!^.*$!acct:john.doe@example.com!" .

   Note that in the first record, the revealed information is limited to
   the domain of the service provider serving that user, as the userpart
   of the 'acct' URI simply replicates the phone number.

6.  DNS Considerations

   There may not be any "E2U+acct" NAPTRs returned in response to the
   original ENUM query on the requested telephone number, but other
   terminal ENUM NAPTRs that include tel: URLs [RFC3966] (e.g.,
   "voice:tel", "pstn:tel", "sms:tel", or "mms:tel" -- see [RFC6118])
   may be present.

   The application that made that ENUM query may choose to resubmit ENUM
   queries for any E.164 numbers included in those returned terminal
   NAPTRs.  Doing so may cause a query loop (e.g., the ENUM records
   returned from subsequent queries may refer to the telephone number
   already considered).  If applications choose to perform subsequent
   ENUM queries using telephone numbers retrieved from earlier queries,
   these applications MUST be aware of the potential for query loops and
   MUST be prepared to abort the set of queries if such a loop is
   detected.

   This issue is similar to the referential loop issue caused by
   processing non-terminal NAPTR queries, as mentioned in Section 5.2.1
   of [RFC6116], and a similar technique to mitigate this issue can be
   used; an application searching for records with "acct" Enumservice
   may consider that submitting a chain of more than 5 ENUM queries
   without finding such a record indicates that a referential loop has
   been entered, and the chain of queries SHOULD be abandoned.

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7.  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 Public Switched
   Telephone Network (PSTN) Enumservice data, this information would be
   visible to anyone anonymously.

   Carriers, service providers, and other users may choose not to
   publish such information in the public e164.arpa tree.  They may
   instead simply publish this in an internal ENUM infrastructure that
   is only able to be queried by trusted elements of their network, thus
   limiting threats.

   For security considerations that apply to all Enumservices, please
   refer to [RFC6116], Section 7.

   It is important to note that the ENUM record itself does not need to
   contain any personal information but only contains a pointer to an
   account identifier.  This identifier may be queried to discover
   pointers to personal information (e.g., social-network information)
   endpoints, and an authorization mechanism may be in place in that
   context with any level of granularity; these topics are out of scope
   for this document.

   Technically, ENUM records themselves could contain pointers to the
   same endpoints.  However, the visibility of ENUM records cannot be
   controlled based on the requesting entity.  In that context, the
   simple mapping of the phone number to the account identifier,
   notwithstanding the disclosure of the association itself, still
   enables the reuse of more advanced access policies.

   Revealing an 'acct' URI by 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.

   Unlike a traditional telephone number, the endpoint identified by an
   'acct' URI may require that requesting entities provide cryptographic
   credentials for authentication and authorization before messages are
   exchanged.  ENUM can actually provide far greater protection from
   unwanted requesting entities than does the existing PSTN, despite the
   public availability of ENUM records.

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   More serious security concerns are associated with potential attacks
   against an underlying system (for example, a social-network system)
   using the 'acct' URI.  For this reason, the underlying system should
   have a number of security requirements that call for authentication,
   integrity, and confidentiality properties, and similar measures to
   prevent such attacks.  This is out of scope for this document.

8.  IANA Considerations

   Per this document, IANA has registered the Enumservice with Type
   "acct" according to the definitions in this document, [RFC6116], and
   [RFC6117].

   Details of the registration are given in Section 4.

9.  References

9.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <http://www.rfc-editor.org/info/rfc1034>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3966]  Schulzrinne, H., "The tel URI for Telephone Numbers",
              RFC 3966, DOI 10.17487/RFC3966, December 2004,
              <http://www.rfc-editor.org/info/rfc3966>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC6116]  Bradner, S., Conroy, L., and K. Fujiwara, "The E.164 to
              Uniform Resource Identifiers (URI) Dynamic Delegation
              Discovery System (DDDS) Application (ENUM)", RFC 6116,
              DOI 10.17487/RFC6116, March 2011,
              <http://www.rfc-editor.org/info/rfc6116>.

   [RFC6117]  Hoeneisen, B., Mayrhofer, A., and J. Livingood, "IANA
              Registration of Enumservices: Guide, Template, and IANA
              Considerations", RFC 6117, DOI 10.17487/RFC6117,
              March 2011, <http://www.rfc-editor.org/info/rfc6117>.

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   [RFC6118]  Hoeneisen, B. and A. Mayrhofer, "Update of Legacy IANA
              Registrations of Enumservices", RFC 6118,
              DOI 10.17487/RFC6118, March 2011,
              <http://www.rfc-editor.org/info/rfc6118>.

   [RFC7565]  Saint-Andre, P., "The 'acct' URI Scheme", RFC 7565,
              DOI 10.17487/RFC7565, May 2015,
              <http://www.rfc-editor.org/info/rfc7565>.

9.2.  Informative References

   [OMA-SNeW]
              Open Mobile Alliance, OMA-ER-SNeW-V1_0, "Social Network
              Web Enabler", August 2013,
              <http://technical.openmobilealliance.org/Technical/
              release_program/snew_v1_0.aspx>.

Acknowledgements

   The authors would like to thank Gonzalo Salgueiro, Paul Jones,
   Lawrence Conroy, Enrico Marocco, Bert Greevenbosch, and Bernie
   Hoeneisen for their valuable feedback to improve this document.

Authors' Addresses

   Laurent-Walter Goix
   Econocom-Osiatis Ingenierie
   75 cours Albert Thomas
   69003 Lyon
   France

   EMail: laurent.goix@econocom-osiatis.com

   Kepeng Li
   Individual
   969 Wenyixi Road
   311121 Hangzhou
   China

   EMail: kepeng.likp@gmail.com

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