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rfc:rfc4237

Network Working Group G. Vaudreuil Request for Comments: 4237 Lucent Technologies Category: Standards Track October 2005

                 Voice Messaging Directory Service

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 (2005).

Abstract

 This document provides details of the Voice Profile for Internet Mail
 (VPIM) directory service.  The service provides the email address of
 the recipient that is given a telephone number.  It optionally
 provides the spoken name of the recipient and the media capabilities
 of the recipient.
 The VPIM directory Schema provides essential additional attributes to
 recreate the voice mail user experience using standardized
 directories.  This user experience provides, at the time of
 addressing, basic assurances that the message will be delivered as
 intended.  This document combines two earlier documents, one from
 Anne Brown and one from Greg Vaudreuil, that define a voice messaging
 schema into a single working group submission.

Vaudreuil Standards Track [Page 1] RFC 4237 Voice Messaging Directory Service October 2005

Table of Contents

 1. Scope ...........................................................2
    1.1. Design Goals ...............................................2
    1.2. Performance Constraints ....................................2
    1.3. Scaling Constraints ........................................3
    1.4. Reliability Constraints ....................................3
 2. The VPIMUser Directory Schema ...................................3
    2.1. vPIMTelephoneNumber ........................................4
    2.2. vPIMRfc822Mailbox ..........................................4
    2.3. vPIMSpokenName .............................................4
    2.4. vPIMTextName ...............................................5
    2.5. vPIMSupportedAudioMediaTypes ...............................5
    2.6. vPIMSupportedMessageContext ................................5
    2.7. vPIMExtendedAbsenceStatus ..................................6
    2.8. vPIMSupportedUABehaviors ...................................6
    2.9. vPIMMaxMessageSize .........................................7
    2.10. vPIMSubMailboxes ..........................................8
 3. Security Considerations .........................................8
 4. IANA Considerations .............................................9
    4.1. Object Identifiers .........................................9
    4.2. Object Identifier Descriptors ..............................9
 5. References .....................................................10
    5.1. Normative References ......................................10
    5.2. Informative References ....................................10

1. Scope

1.1. Design Goals

 The VPIM directory Schema (VPIMDIR) is accessed from outside the
 enterprise or service provider domain using the recipient's telephone
 number.

1.2. Performance Constraints

 Once the identity of the VPIM directory server is known, the email
 address, capabilities, and spoken name confirmation information can
 be retrieved.  This query is expected to use LDAP [LDAP], a
 connection-oriented protocol.  The protocol transaction includes
 multiple packet round-trips to execute the query and retrieval and is
 considered to be the highest latency element of the messaging
 service.  Further, retrieval of the confirmation information may
 require the return of a spoken name segment of up to 20kbytes (5
 seconds at 4kbytes/second).  Over a sufficiently engineered Internet
 connection, a 1250 ms response time is believed to be achievable over
 the Internet at large.

Vaudreuil Standards Track [Page 2] RFC 4237 Voice Messaging Directory Service October 2005

1.3. Scaling Constraints

 A service provider's namespace is expected to include entries for
 tens of millions of subscribers in a flat namespace based on the VPIM
 inter-domain address form: telephone_number@domain_name.  A large
 corporation may have a hundred-thousand entries, while a large
 service provider may have tens of millions of entries in a single
 domain.  It is expected that there will be a single public address
 validation service for a given service provider's network.  It is
 believed that existing directory technology, including horizontal
 scalability through replication, will provide sufficient transaction
 throughput within the required latency requirements to address this
 need.  The only fundamental, new requirement this application imposes
 on directory servers, beyond similar existing services, is the
 ability to return the recipient's spoken name.  Preliminary
 investigation suggests that storage and retrieval of a spoken name
 will not add appreciable latency; however, it will add to the need
 for storage capacity.

1.4. Reliability Constraints

 DNS provides well-documented redundancy and load-balancing
 capabilities for the VPIMDIR.  However, the latency requirements to
 the end-user may not permit client-side fail-over to a secondary
 server and may require the directory server to be implemented as a
 high-availability service.

2. The VPIMUser Directory Schema

    (IANA-ASSIGNED-OID.1 NAME 'vPIMUser'
            SUP 'top'
            AUXILIARY
            MUST ( vPIMRfc822Mailbox $
                   vPIMTelephoneNumber )
            MAY  ( vPIMSpokenName $
                   vPIMSupportedUABehaviors $
                   vPIMSupportedAudioMediaTypes $
                   vPIMSupportedMessageContext $
                   vPIMTextName $
                   vPIMExtendedAbsenceStatus $
                   vPIMMaxMessageSize $
                   vPIMSubMailboxes ) )
 When present, the vPIMUser object contains information useful for
 verifying that the dialed telephone number corresponds to the
 intended recipient.  This object also provides capability information
 and mailbox status information useful for guiding composition by the
 sender and for setting delivery expectations at sending time.

Vaudreuil Standards Track [Page 3] RFC 4237 Voice Messaging Directory Service October 2005

2.1. vPIMTelephoneNumber

 The attribute vPIMTelephoneNumber is the full E.164 form of the
 telephone number [E164], including any sub-addressing portion.  The
 normal search will be for this attribute.
    (IANA-ASSIGNED-OID.2.1 NAME 'vPIMTelephoneNumber'
                        EQUALITY caseIgnoreMatch
                        SYNTAX 1.3.6.1.4.1.1466.115.121.1.44{20} )
 Example: A North American telephone number with the sub address of 12
 would be represented as "+12145551212+12".
 Note that vPIMTelephoneNumber is, by default, a multi-valued
 attribute.  But if an entry has multiple values for this attribute,
 those values MUST be distinct from each other in the telephone number
 portion.  It is expected that each submailbox of a single telephone
 number will have its own vPIMUser entry.
 The vPIMTelephoneNumber differs from telephoneNumber in [LDAP] in its
 support for sub-addressing information and its use as a voice
 messaging address.  In most cases, these values will be the same.
 The telephone number is stored with no parenthesis, spaces, dots, or
 hyphens.  The leading '+' and the '+' delineating the submailbox are
 required markup.

2.2. vPIMRfc822Mailbox

 The attribute vPIMRfc822Mailbox stores the inter-domain SMTP address
 of the voice mailbox associated with a given telephone number.  It is
 defined as a distinct attribute to distinguish it from the
 rfc822Mailbox attribute that may be used for other purposes.
 Although it would be preferable to define vPIMRfc822Mailbox as a
 subtype of rfc822Mailbox, it is defined here as an entirely new
 attribute because some directory implementations do not support sub-
 typing.
    (IANA-ASSIGNED-OID.2.2 NAME 'vPIMRfc822Mailbox'
                      EQUALITY caseIgnoreIA5Match
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.26{256} )

2.3. vPIMSpokenName

 The vPIMSpokenName attribute is an octet string and MUST be encoded
 in 32 kbit/s ADPCM exactly, as defined by [32KADPCM].  vPIMSpokenName
 shall contain the spoken name of the user in the voice of the user.
 The length of the spoken name segment MUST NOT exceed five seconds.

Vaudreuil Standards Track [Page 4] RFC 4237 Voice Messaging Directory Service October 2005

 Private or additional encoding types are outside the scope of this
 version.
    (IANA-ASSIGNED-OID.2.3 NAME 'vPIMSpokenName'
                      EQUALITY octetStringMatch
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.40{20000}
                      SINGLE-VALUE )

2.4. vPIMTextName

 The text name is designed to be consistent with the unstructured
 text name databases used for calling name delivery service of
 caller ID.
    (IANA-ASSIGNED-OID.2.4 NAME 'vPIMTextName'
                      EQUALITY caseIgnoreMatch
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.15{20}
                      SINGLE-VALUE )

2.5. vPIMSupportedAudioMediaTypes

 The vPIMSupportedAudioMediaTypes attribute indicates the type(s) of
 audio encodings that can be received at the address specified in
 vPIMRfc822Mailbox.
    (IANA-ASSIGNED-OID.2.5 NAME 'vPIMSupportedAudioMediaTypes'
                      EQUALITY caseIgnoreIA5Match
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
 This is a multi-value attribute.  The allowable values for this
 attribute are the MIME audio subtypes registered with IANA.  Non-
 standard and private encoding types must be indicated by prepending
 the new type name with either "X-" or "x-".
 Because ADPCM is a required format, the audio32kadpcm value must be
 listed if this attribute is present.

2.6. vPIMSupportedMessageContext

 The message context provides guidance to the sender about the message
 contexts the recipient is likely to accept.  Message context provides
 less precise information about a given recipient's capabilities than
 a list of media types.  However, given the growing role of media-
 conversion gateways, the context indicator provides more useful
 guidance to a sender in a "unified messaging" environment.

Vaudreuil Standards Track [Page 5] RFC 4237 Voice Messaging Directory Service October 2005

    (IANA-ASSIGNED-OID.2.6 NAME 'vPIMSupportedMessageContext'
                      EQUALITY caseIgnoreIA5Match
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
 This is a multi-value attribute.  The set of valid message context
 values is defined in [CONTEXT].

2.7. vPIMExtendedAbsenceStatus

 It is common to have an attribute that indicates to the subscriber
 whether the recipient is accepting messages during his absence.  This
 feature -- called "extended absence" -- provides an advisory message
 at sending time.  It is similar in concept to "vacation notices"
 common for textual email, but has its own cultural and operational
 nuances.
    (IANA-ASSIGNED-OID.2.7 NAME 'vPIMExtendedAbsenceStatus'
                      EQUALITY caseIgnoreIA5Match
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.26
                      SINGLE-VALUE )
 The three values defined are:
          "Off", "On", "MsgBlocked"
 "Off" indicates that the recipient either does not support extended
 absence or has not set such an indicator.  "Off" is the default
 condition if this attribute is not returned.
 "On" indicates that the recipient has set an extended absence
 indicator, but the mailbox is still accepting messages for review at
 an unspecified future time.
 "MsgBlocked" indicates that the recipient has set an extended absence
 indicator and the mailbox is currently configured to reject incoming
 messages.  Messages SHOULD NOT be sent to the recipient if this value
 is returned in the vPIMExtendedAbsenceStatus attribute.

2.8. vPIMSupportedUABehaviors

 Internet mail does not provide facilities for the sender to know
 whether the recipient supports a number of optional features that can
 be requested or indicated in the RFC822 headers.  This attribute
 provides a list of the attributes, considered optional by VPIM and
 other vendor-specific attributes, that may be supported by the
 recipient.  If this attribute is not supported, only those attributes

Vaudreuil Standards Track [Page 6] RFC 4237 Voice Messaging Directory Service October 2005

 listed as mandatory in VPIM are assumed to be supported.  Undisclosed
 behaviors may be indicated in the RFC822 message; however, there is
 no assurance by the receiving system of their support.
    (IANA-ASSIGNED-OID.2.8 NAME 'vPIMSupportedUABehaviors'
                      EQUALITY caseIgnoreIA5Match
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 )
 The following behaviors are defined:
          MessageDispositionNotification
          MessageSensitivity
          MessageImportance
 The presence of the MessageDispositionNotification value indicates
 that the recipient will send an MDN in response to an MDN request.
 MessageSensitivity indicates that the recipient fully supports the
 sensitivity indication as defined in VPIM [VPIMV2].
 MessageImportance indicates that the recipient fully supports the
 importance indication as defined in VPIM [VPIMV2].
 These may be further extended without standardization to include
 proprietary user interface functional extensions.  These proprietary
 extension values must be prefixed with an "X-" or "x-".

2.9. vPIMMaxMessageSize

 At the time of composition, the message can be checked for acceptable
 length using the maximum message size attribute.  Maximum message
 size is an attribute usually configured by policy of the receiving
 system, typically in units of minutes.  While ESMTP provides a
 mechanism to determine if a message is too long in bytes, it is an
 unreliable guide for the composer when multiple encodings, multiple
 media, or variable bit-rate encodings are supported.
    (IANA-ASSIGNED-OID.2.9 NAME 'vPIMMaxMessageSize'
                      EQUALITY integerMatch
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.27
                      SINGLE-VALUE )
 The attribute indicates the maximum message length in seconds that
 the receiving mailbox may receive.

Vaudreuil Standards Track [Page 7] RFC 4237 Voice Messaging Directory Service October 2005

2.10. vPIMSubMailboxes

 This attribute indicates the presence of sub-mailboxes for the
 queried telephone number.  This information may be used to provide a
 post-dial sub-addressing menu to the sender.
    (IANA-ASSIGNED-OID.2.10 NAME 'vPIMSubMailboxes'
                      EQUALITY numericStringMatch
                      SYNTAX 1.3.6.1.4.1.1466.115.121.1.36{4} )
 The allowable values include a list of sub-mailbox numbers with a
 numeric range of 1-9999.  The user interface may use this information
 to prompt the sender to select a sub-mailbox.  Spoken names
 associated with each sub-mailbox may be individually retrieved by
 subsequent queries to the recipient's VPIMDIR service.

3. Security Considerations

 The following are known security issues.
 1) Service provider customer information is very sensitive,
    especially in this time of local phone competition.  Service
    providers require maximum flexibility to protect this data.
    Because of the dense nature of telephone number assignments, this
    data is subject to "go fish" queries via repeated LDAP queries to
    determine a complete list of current or active messaging
    subscribers.  To reduce the value of this retrieved data, service
    providers may limit disclosure of data that is useful for
    telemarketing, such as the textual name, and may disclose only
    information useful to the sender, such as the recipient's spoken
    name, a data element that is much harder to auto-process.
 2) In many countries, there are privacy laws or regulations that
    prohibit disclosure of certain kinds of descriptive information
    (e.g., text names).  Hence, server implementors are encouraged to
    support DIT structural rules and name forms [LDAPMODELS] as these
    provide a mechanism for administrators to select appropriate
    naming attributes for entries.  Administrators are encouraged to
    use these mechanisms, access controls, and other administrative
    controls, which may be available to restrict use of attributes
    containing sensitive information when naming entries.
 3) The LDAP directory service needs to be secured properly for this
    intended use.  [LDAPAUTH] describes a number of considerations
    that apply in this use.  In particular, this service provides
    unauthenticated, public access to directory data, and as such, it
    is vulnerable to attacks that redirect the query to a rogue server
    and offer malicious data.

Vaudreuil Standards Track [Page 8] RFC 4237 Voice Messaging Directory Service October 2005

4. IANA Considerations

 Reference RFC 3383 "Internet Assigned Numbers Authority (IANA)
 Considerations for the Lightweight Directory Access Protocol (LDAP)"
 [LDAPREG].

4.1. Object Identifiers

 IANA has registered an LDAP Object Identifier for use in this
 technical specification, according to the following template:
 Subject: Request for LDAP OID Registration
 Person & email address to contact for further information:
    Greg Vaudreuil (gregv@ieee.org)
 Specification: RFC 4237
 Author/Change Controller: IESG
 Comments:
 The assigned OID will be used as a base for identifying a number of
 schema elements defined in this document.

4.2. Object Identifier Descriptors

 IANA has registered the LDAP Descriptors used in this technical
 specification, as detailed in the following template:
 Subject: Request for LDAP Descriptor Registration Update
 Descriptor (vPIM): see comment
 Object Identifier: see comment
 Person & email address to contact for further information:
    GregV@ieee.org
 Usage: see comment
 Specification: RFC 4237
 Author/Change Controller: IESG
 Comments:

Vaudreuil Standards Track [Page 9] RFC 4237 Voice Messaging Directory Service October 2005

 The following descriptors have been added:
 NAME                            Type    OID
 --------------                  ----    ------------
 vPIMUser                         O      IANA-ASSIGNED-OID.1.1
 vPIMRfc822Mailbox                A      IANA-ASSIGNED-OID.2.1
 vPIMTelephoneNumber              A      IANA-ASSIGNED-OID.2.2
 vPIMSpokenName                   A      IANA-ASSIGNED-OID.2.3
 vPIMSupportedUABehaviors         A      IANA-ASSIGNED-OID.2.4
 vPIMSupportedAudioMediaTypes     A      IANA-ASSIGNED-OID.2.5
 vPIMSupportedMessageContext      A      IANA-ASSIGNED-OID.2.6
 vPIMTextName                     A      IANA-ASSIGNED-OID.2.7
 vPIMExtendedAbsenceStatus        A      IANA-ASSIGNED-OID.2.8
 vPIMMaxMessageSize               A      IANA-ASSIGNED-OID.2.9
 vPIMSubMailboxes                 A      IANA-ASSIGNED-OID.2.10
 Where Type A is Attribute and Type O is ObjectClass

5. References

5.1. Normative References

 [LDAP]       Hodges, J. and R. Morgan, "Lightweight Directory Access
              Protocol (v3): Technical Specification", RFC 3377,
              September 2002.
 [32KADPCM]   Vaudreuil, G. and G. Parsons, "Toll Quality Voice - 32
              kbit/s Adaptive Differential Pulse Code Modulation
              (ADPCM) MIME Sub-type Registration", RFC 3802, June
              2004.
 [CONTEXT]    Burger, E., Candell, E., Eliot, C., and G. Klyne,
              "Message Context for Internet Mail", RFC 3458, January
              2003.
 [E164]       CCITT Recommendation E.164 (1991), Telephone Network and
              ISDN Operation, Numbering, Routing and Mobile Service -
              Numbering Plan for the ISDN Era.

5.2. Informative References

 [VPIMV2]     Vaudreuil, G. and G. Parsons, "Voice Profile for
              Internet Mail - version 2 (VPIMv2)", RFC 3801, June
              2004.

Vaudreuil Standards Track [Page 10] RFC 4237 Voice Messaging Directory Service October 2005

 [LDAPREG]    Zeilenga, K., "Internet Assigned Numbers Authority
              (IANA) Considerations for the Lightweight Directory
              Access Protocol (LDAP)", BCP 64, RFC 3383, September
              2002.
 [LDAPAUTH]   Wahl, M., Alvestrand, H., Hodges, J., and R. Morgan,
              "Authentication Methods for LDAP", RFC 2829, May 2000.
 [LDAPMODELS] Zeilenga, K., "LDAP: Directory Information Models" Work
              in Progress, February 2005.

Acknowledgements

 This directory schema builds upon the earlier work of Carl Malamud
 and Marshall Rose in their TPC.INT remote printing experiment and the
 work lead by Anne Brown as part of the EMA voice messaging
 committee's directory effort.  Anne Brown has provided important
 leadership and was a co-author of the original version of this
 document.
 Bernhard Elliot, working with the TMIA, has provided most of the
 organizational impetus to get this project moving, which was a
 substantial task given the sometimes slow and bureaucratic nature of
 the voice mail industry and regulatory environment.
 Thanks to Dave Dudley and the Messaging Alliance (TMA) for their
 early work in pioneering a shared directory service for voice
 messaging and their continuing efforts to apply that work to this
 effort.
 Greg White and Jeff Bouis, both of Lucent Technologies, provided
 invaluable assistance in reviewing and sanity checking.  Countless
 errors and inconsistencies were corrected with their diligent review.
 As chairman of the VPIM working group, Glenn Parsons has provided
 essential support over the many years this document has been in
 development.

Vaudreuil Standards Track [Page 11] RFC 4237 Voice Messaging Directory Service October 2005

Author's Address

 Please send comments on this document to the VPIM working group
 mailing list <vpim@ietf.org>.
 Gregory M. Vaudreuil
 Lucent Technologies
 9489 Bartgis Ct
 Frederick, MD 21702
 EMail: GregV@ieee.org

Vaudreuil Standards Track [Page 12] RFC 4237 Voice Messaging Directory Service October 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 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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Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Vaudreuil Standards Track [Page 13]

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