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     Internet Draft                                       Greg Vaudreuil
     Expires in six months                           Lucent Technologies
                                                           July 13, 2000
                         Voice Message Routing Service
  Status of this Memo
     This document is an Internet-Draft and is in full conformance with all
     provisions of Section 10 of RFC2026.
     This document is an Internet Draft.  Internet Drafts are working
     documents of the Internet Engineering Task Force (IETF), its Areas,
     and its Working Groups.  Note that other groups may also distribute
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     ftp.isi.edu (US West Coast).
  Copyright Notice
     Copyright (C) The Internet Society (2000).  All Rights Reserved.
     This Internet-Draft is in conformance with Section 10 of RFC2026.
     Voice messaging is traditionally addressed using telephone number
     addressing. This document describes two techniques for routing voice
     messages based on a telephone number.  The VPIM Directory service
     provides a mechanism to map between a telephone number and a VPIM
     email address and confirm that the address is both valid and the
     assocaited with the intended recipient.  However this service will
     take time become widely deployed in the nearest term.  This document
     also describes a more limited send-and-pray service useful simply to
     route and deliver message using only the existing DNS mail routing
     facilies, the ENUM telephone number resolution service, and a set of
     pre-defined address creation rules.
     Please send comments on this document to the VPIM working group
     mailing list <vpim@lists.neystadt.org>

     Internet Draft            VPIM Routing                July 13, 2000
  Working Group Summary
     This is a submission to the IETF VPIM working group.
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     Internet Draft            VPIM Routing                July 13, 2000
  Table of Contents
  1.   ABSTRACT ..........................................................4
  2.   DESIGN GOALS ......................................................4
  3.   THE COMPLETE SERVICE ..............................................5
    3.1  VPIM Directory Discovery ........................................5
    3.2  Address Query ...................................................5
  4.   THE BASIC SERVICE .................................................6
    4.1  Address Construction ............................................6
    4.2  Inter-domain Message Routing ....................................7
    4.3  Intra-domain Message Routing ....................................7
  5.   SECURITY CONSIDERATIONS ...........................................9
  6.   REFERENCES ........................................................9
  7.   ACKNOWLEDGMENTS ..................................................10
  8.   COPYRIGHT NOTICE .................................................10
  9.   AUTHORS' ADDRESSES ...............................................10
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  1. Abstract
  2. Design Goals
     This profile is intended to provide a range of functional capabilities
     for message routing based on one of two mechanisms.  The most complete
     service should the ENUM address resolution service to determine the
     VPIM directory, and then use LDAP to retreive the VPIM email address
     to use for message routing.
     The most basic send-and-pray message service uses only address
     construction rules, the ENUM service, and MX records to route the
     message to the intended recipient's domain.  The intelligence to
     further route the message to the intended recipient is placed within
     the message routing system of the recipient's domain.
     The basic mechanism may be used even when there is a VPIM directory
     service avaiable.  The basic service is useful when LDAP queries are
     not available, such as may be the case for disconnected mobile
     terminals or because of firewall or information security policies.
     The basic mechanism should facilitate the routing of VPIM messages to
     a suitable internal destination with a minimum of configuration. .  It
     is an important goal to avoid any content-processing to determine the
     nature of the message and it's internal destination.  It should be
     possible at a minimum to establish a simple mail forwarding rule to
     send all inbound VPIM message to a designated system while
     facilitating the routing of FAX, SMS, or other telephone addressed
     messages to other potentially different systems
     It is a goal that the mechanisms outlined in this document be
     extensible for all store-and-forward, telephone-number addressed
     messaging services.
     It is a goal that the VPIM directory discovery and VPIM Directory
     query steps ocure within the timing constraints for user interfaces in
     PSTN networks.  In general that constraint can be generalized to be a
     two second response %95 of the time.
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  3. The Complete Service
     For the complete VPIM message routing service, the sending client
     should query the VPIM directory for the VPIM-specific email address.
     The client should use the ENUM service to retrieve the identity of the
     VPIM Directory to query, and then query that server for the email
     address and any additional attributed desired.
  3.1 VPIM Directory Discovery
     The VPIM directory server is found by querying DNS for the SRV record
     associated with the domain name of the recipient as found in the
     address resolution step.
     The DNS query name is created by appending the VPIM service request
     "_VPIMDIR._TCP" to the reverse-dotted telephone number based domain
     name as described by [ENUM].  The telephone number used for the
     directory location SHOULD NOT contain sub-address information. See
          Note: There are potential interactions and an increase in
          provisioning burden when using a domain name with more levels
          than necessary, especially when using CNAME redirection services.
          In the absence of better understanding, this is best avoided.
          See [ENUMOPS]
            Query: _VPIM._TCP.
            Response:    SRV=vpimdir1.example.com  weight=10 preference=10
                         SRV=vpimdir2.example.com  weight=20 preference=10
     Given the lack of elegant client-side redundancy for LDAP, and the
     real-time requirements for a response, the VPIMDIR service should be
     provided on a high-availability server to ensure the service is
     available on the first try.
  3.2 Address Query
     Once the VPIM directory is discovered, the client should issue a LDAP
     query for the vPIMrFC822Address. That is the address that should be
     used as the value for both the RFC822 to: field and the SMTP RCPT TO
     command. See [VPIMDIR]
     To facilitate higher system availability, it is recommended that
     VPIMDIR servers be deployed in redundant sets. These servers should be
     listed in the SRV records with various weightings.  The querying
     system should attempt a connection to the lowest weight VPIMDIR
     server.  If it is down, the second should be contacted.
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  4. The Basic Service
     The basic service relies upon address creation rules to mechanically
     construct an address that may be routed by the existing infrastructure
     to the recipient's domain.  In the recipient's domain, the
     machanically constructed address may be further routed using intra-
     domain mail routing techniques such as those defined in [LASER].
     To facilitate a full range of intra-domain routing options, the
     constructed email address should contain both the recipients telephone
     number and an indication that the message is a VPIM message.  For ease
     of processing in the recipients intra-domain mail routing system, the
     indication that the message is a VPIM message should be in the domain
     name portion.
     Note, that no validation that the constructed address is valid, nor
     that the constructed address corresponds to the intended recipient.
     Because no capabilities information is provided about the recipient,
     messages sent with this mechaism SHOULD be sent using only the least-
     common denominator media and content types of the intended message
  4.1 Address Construction
     Mechanically construct an email address using only an algorithm
     specific to the messaging service.  For VPIM, the algorithm is as
     1) Normalize the telephone number into E.164 form. Presentation
     information such as spaces, prenthesis, periods, and dashes MUST be
     stripped.  Sub-addresses if known and explicitly indicated should be
     appended to the address using the "+" sign. Construct the local part
     of the email address by prefixing a "+" sign to the E164 telephone
            +19727331212  (A Dallas, US based recipient)
            +441819031212+2  (A Wembly, UK based recipient)
     2) Construct the domain name portion of the address from the telephone
     number.  The sub-address does not affect the inter-domain routing of a
     message. Strip the sub-address portion of the telephone number,
     reverse and dot-stuff the digits consistent with the ENUM
     specification.  Prefix the service selector "_VPIM" to the address and
     append the suffix "e164.arpa".
     3) Concatentate the local part and the domain portion with the "@"
     symbol to yield the recipients basic VPIM address.
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        This is the address that should be used as the value for both the
        RFC822 to: field and the SMTP RCPT TO command.
  4.2 Inter-domain Message Routing
     The inter-domain routing of a constructed VPIM address is mechanically
     indistinguishable from existing email routing.  No changes to the
     infrastructure ar required.  The sending system consults the Domain
     name system for a MX record corresponding to the domain name and
     forwards the message to the indicated system.
     It is through the ENUM service that the MX records are provisioned for
     specific telephone number or whole blocks of delegated telephone
     numbers.  Using the longest-match algorithms of DNS, the DNS routing
     system may be service-ignostic and does not need to have individual MX
     records for each service-specific sub-domain.  However, if it is
     desired to send messages addressed with a given service to the mail
     server of a different domain, a service-specific MX record may be
     provisioned on a per-telephone number basis.  See [ENUMOPS] for a more
     complete description of the structure of the ENUM service.
  4.3 Intra-domain Message Routing
     Within the recipient's domain, the message may be further routed to
     the appropriate messaging system. Two general mechanisms may be used
     to further route the message to the intended system within a network.
          Note: This section is strictly informational.  The mechanisms
          for intra-domain routing are an internal matter for the domain
          and do not affect the protocol.  However, an understanding of
          common intra-domain routing techniques is essential to the
          mechanical creation of a useful address.
  4.3.1 LASER Powered / Directory Enabled Routing
     Various proprietary directory mechanisms and the emerging LASER
     standard mechanism provide a means for a inbound mail router of the
     recipients domain to send a message to the appropriate internal mail
     host.  In many cases, the local part of the address is used to query
     for an internal mail address.  That internal mail address is
     substituted for the RCPT TO address and used to deliver the message to
     the recipient mailbox.  Note that the mailbox does not need to have
     any knowledge of the mechanically constructed telephone number based
  4.3.2 Service-based Mail Routing
     Alternately, a mail gateway may simply send all voice messages into a
     separate messaging system.  That system may be a single voice
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     messaging server or a service-specific gateway into a larger
     telephone-number based voice-messaging network.
     Such a mail gateway may be provisioned with a simple rule or small set
     of rules to forward all messages of a given service type to a pre-
     defined server.  This rule would check for the service name "_VPIM" as
     a prefix to the domain name to re-route messages.  In many cases, such
     as with SMS messaging to mobile phones, this server may external to
     the customers network.
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  5. Security Considerations
     There is little information disclosed to the sender of a message that
     is not already disclosed using standard email protocols beyond the
     ability to probe via send-and-fail the existance of a reachable
     account associated with a telephone number, and via the NDN, determine
     in which domain the account resides.
     However, the use of a simple algorithm to create routeable email
     addresses from telephone numbers provides bulk-emailers the
     capablities to send email to a large set of recipients where only the
     telephone number is known or where telephone numbers are guessed.
  6. References
  [E164] CCITT Recommendation E.164 (1991), Telephone Network and ISDN
      Operation, Numbering, Routing and Mobile Service - Numbering Plan for
      the ISDN Era.
  [VPIM2] Vaudreuil, Greg, Parsons, Glen, "Voice Profile for Internet
      Mail, Version 2", Work-in-Progress, July 2000.
  [VPIMDIR] A. Brown and G. Vaudreuil "VPIM Directory Schema", work-in-
      progress, July 2000.
  [ENUM] P. Faltstrom "E.164 number and DNS", Work-in-Progress, July 2000.
  [ENUMOPS] A. Brown and G. Vaudreuil "ENUM Service Specific Provisioning:
      Principles of Operation", Work-in-Progress, July 2000.
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  7. Acknowledgments
  8. Copyright Notice
     "Copyright (C) The Internet Society (2000). All Rights Reserved.
     This document and translations of it may be copied and furnished to
     others, and derivative works that comment on or otherwise explain it
     or assist in its implementation may be prepared, copied, published and
     distributed, in whole or in part, without restriction of any kind,
     provided that the above copyright notice and this paragraph are
     included on all such copies and derivative works.  However, this
     document itself may not be modified in any way, such as by removing
     the copyright notice or references to the Internet Society or other
     Internet organizations, except as needed for the  purpose of
     developing Internet standards in which case the procedures for
     copyrights defined in the Internet Standards process must be followed,
     or as required to translate it into languages other than English.
     The limited permissions granted above are perpetual and will not be
     revoked by the Internet Society or its successors or assigns.
     This document and the information contained herein is provided on an
  9. Authors' Addresses
     Gregory M. Vaudreuil
     Lucent Technologies,
     17080 Dallas Parkway
     Dallas, TX  75248-1905
     United States
     Phone/Fax: +1-972-733-2722
     Email: GregV@ieee.org
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