Internet Draft Greg Vaudreuil Expires in six months Lucent Technologies December 1, 1999 Voice Messaging Directory Service: Principles of Operation 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 working documents as Internet Drafts. Internet Drafts are valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet Drafts as reference material or to cite them other than as a "work in progress". The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. This Internet-Draft is in conformance with Section 10 of RFC2026. Overview This document outlines the principles for the operation of an experimental telephone number directory service. This service provides for the resolution of telephone number address to domain name address, address confirmation and capabilities discovery, and intra- domain messaging routing. This directory service uses a combination of DNS and LDAP queries. The experiment is conducted using voice messaging in the North American dialing plan as the prototype application. Please send comments on this document to the author, Greg Vaudreuil . Internet Draft VPIM Directory December 1, 1999 Working Group Summary This document is not the product of an IETF working group. It documents a inter-company voice message interchange experiment conducted over the Internet as a project of the Telemessaging Industry Association (TMIA) http://www.tmia.org. The TMIA is a consortium of large North American wireline and wireless telephone companies. Vaudreuil, Parsons Expires 5/1/00 [Page 2] Internet Draft VPIM Directory December 1, 1999 Table of Contents 1. ABSTRACT ............................................................4 2. SCOPE ...............................................................5 2.1Design Goals ......................................................5 3. SYSTEM DESCRIPTION ..................................................6 3.1Time Constraints ..................................................6 4. ADDRESS RESOLUTION SERVICE ..........................................7 4.1E164.int Domain ...................................................8 5. INTER-DOMAIN MESSAGE ROUTING ........................................8 6. ADDRESS CONFIRMATION SERVICE ........................................8 6.1Address Validation Server Discovery ...............................9 6.2Address Validation LDAP Query .....................................9 7. INTRA-DOMAIN MESSAGE ROUTING SERVICE ................................9 8. SECURITY CONSIDERATIONS ............................................10 9. REFERENCES .........................................................10 10.ACKNOWLEDGMENTS ....................................................11 11.COPYRIGHT NOTICE ...................................................11 12.AUTHORS' ADDRESSES .................................................12 Vaudreuil, Parsons Expires 5/1/00 [Page 3] Internet Draft VPIM Directory December 1, 1999 1. Abstract General electronic mail (email) provides a facility for exchanging messages of seemingly arbitrary content. In common email usage, text is the primary media with one or more attachments. A class of special-purpose computers has evolved to provide voice- messaging services. These machines generally interface to a telephone switch and provide call answering and voice messaging services. Message exchange between these voice-mail only systems can best be achieved using VPIM Version 2. Voice messaging uses the ubiquitous telephone as the primary terminal for access and for the sending of messages. As such, the limitations of the numeric keypad must be adequately addressed. The following limitations are addressed by the directory service described in this document: 1) Telephone numbers are the natural identifiers for messages sent from a telephone and to a telephone-based recipient. Internet mail on which VPIM V2 messages are transported use the Domain Name System identifiers. The directory service must translate between these addressing systems. 2) Entry of a telephone number is error-prone. While a mis-typed email address will generally fail to be delivered, a mis-dialed number may more frequently be delivered to the wrong recipient. Confirmation that the dialed number corresponds to the intended recipient is considered an essential part of voice messaging service. 3) Voice terminals are relatively inflexible in the handling of media and encodings. Spawning a helper application is not feasible. Coupled with the strong pressure to adopt ever cheaper and more compact audio encodings, voice messaging requires the ability for the sender to tailor the composition to the capabilities of the recipient. 4) While telephone numbers uniquely identify a recipient in inter- domain space, service providers have needs to name or number the recipient's mailboxes according to more local requirements. A standard for the mapping between the telephone-number-based inter- domain form of the email address to an inter-domain form is required for interoperability between multiple directory and messaging platform vendors. 5) Telephone-based users have a strong expectation for rapid a response to addressing actions. While various "delaying" tone or phrase may extend this (audio hourglass?) time, the accepted normal maximum interval is two seconds with perceived system failure at five seconds. The directory system must provide responses within these tight latency requirements. Vaudreuil, Parsons Expires 5/1/00 [Page 4] Internet Draft VPIM Directory December 1, 1999 2. Scope This document is the first of a set that define the experimental voice messaging directory service. This document discussed design goals and the principles of operation. Subsequent documents detail the schema for the DNS and LDAP portions of the service. 2.1 Design Goals Rapid Deployment through use of existing protocols, products and infrastructure. Leverage existing administrative address assignment and authority delegation hierarchies to accelerate time-to-market. Provide maximum flexibility for a provider to control sensitive directory information made available, while ensuring that message can reliably be exchanged. Vaudreuil, Parsons Expires 5/1/00 [Page 5] Internet Draft VPIM Directory December 1, 1999 3. System Description 3.1 Performance Constraints This directory service is latency critical. For the full set of features, a number of queries must occur within a short time interval, optimally less than two seconds. The following Vaudreuil, Parsons Expires 5/1/00 [Page 6] Internet Draft VPIM Directory December 1, 1999 4. Address Resolution Service The high level directory provides Address Resolution Service (ARS) to map between telephone numbers and routeable Internet email addresses. The phone number is the international E.164 form, and the Email address is the inter-domain form such as 19727332722@voice.SP.net. The Internet Domain Name System provides an ideal technology for this directory due to it's fast, hierarchical structure and distributed administrative model. Earlier experimentation with the TPC.INT remote printing experiment has shown how the hierarchical assignment of telephone numbers can be mapped directly to the hierarchy of domains within the DNS. The ARS directory uses that approach to map any arbitrary telephone number into a single domain name. The telephone number data to populate the highest level entries in the ARS is publicly available. The ITU maintains a list of country codes and the authorities that manage the sub-structure under countries. Within North America, the delegation of phone numbers to the NPA/NXX level is managed by the "Traffic Routing Administration" a cooperative agreement with Telecordia (http://www.trainfo.com). The delegations are made available in a quarterly publication called the Local Exchange Routing Guide (LERG). The LERG is available publicly for a nominal fee. Toll free numbers (800 and 888), ported telephone numbers, and sub- delegation of numbers to enterprises are beyond the scope of this initial directory experiment. Local number portability (LNP) does not change the delegation of phone numbers, but does change their routing. The LNP routing of phone numbers to carriers is a third-level directory in the hierarchy managed by the Number Portability Administrative Center (NPAC) managed under contract by Martian Marrietta (http://www.nanpa.com). While this data is also publicly available, it does require an agreement to receive real-time replication from the master database. Due to cost and time constraints, ported telephone numbers are beyond the scope of this initial experiment, however, they are very important and any viable solution must address the need to receive a correct mapping to a domain name for these number. Within a given service provider, authority for telephone numbers may be further sub-assigned to individual customers, either on a number- by-number, or by telephone number blocks. This delegation is typically private information maintained by each telco. Successful exchange of messages using telephone numbers between enterprises requires that service providers make this information via the directory service. Similar to the infrastructure for LNP, this effort is beyond the scope of the initial voice messaging directory experiment, however, it is a goal to provide the protocol infrastructure necessary to address this need. Vaudreuil, Parsons Expires 5/1/00 [Page 7] Internet Draft VPIM Directory December 1, 1999 4.1 E164.int Domain This document claims the e164.int domain as the root for the telephone numbering hierarchy. The operating entity for the primary server for the duration of the experiment is the NANP DNS authority. That authority has not yet determined, however Lucent Technologies may assume that responsibility for the duration of the experiment or until a more suitable entity can be suckered into it. The North American Numbering Plan (NAMP) subdomain, country code "1" of the E164 will also be operated on an interim basis by the NANP DNS authority. The North American Numbering Plan (NANP) local routing information in the LERG database maps a telephone number prefix to an Operating Company Number (OCN). The OCN is the unique identifier of the local exchange operator that has received the telephone number delegation. This delegation does not change with LNP. The primary name server for the NANP will provide domain name service for the NANP based on a mapping between OCN and the domain name chosen by the operating company. The NANP DNS authority will maintain the registration of the domain name to OCN mapping. Information to Sub-delegate telephone number assignments below a NPA/NXX level within the NANP will be maintained by the NANP DNS authority and made generally available as a DNS referral. 5. Inter-domain Message Routing The high-level directory query provides all the information necessary to route a message from one service provider to another using the existing mail routing infrastructure. Mail routers, firewalls, and redundancy for voice messaging is identical to that deployed for email routing. This inter-domain mail routing is not discussed in detail in this proposal, but uses the mail exchange "MX" routing records in DNS to route a message to one or more appropriate gateways or firewalls. There is no restriction on the nature of the messages routed to these gateways. They may be the same as the general-purpose email gateways. It is up to the receiving system to determine the appropriate destination with their network for a given message. 6. Address Confirmation Service Address validation is the directory step whereby one service provider can inquire of another about the validity of a telephone number for messaging and to receive spoken name confirmation and a set of capabilities of the recipient. This is an optional service. A message sender may send a message to the recipient using the inter- domain form of the email address determined from the address resolution service described above. Address confirmation and capabilities discovery is an additional, higher level of service. Vaudreuil, Parsons Expires 5/1/00 [Page 8] Internet Draft VPIM Directory December 1, 1999 6.1 Address Validation Server Discovery The first step of this directory step is to identify the appropriate directory server of the recipient domain. For this, the DNS provides an extension record called the service record or SRV. This record acts like the MX record in providing a list of servers offering a given service to provide redundancy. For the voice messaging address validation service, the AVS service record is defined. (The details are contained within a companion document). The address validation server is found by querying DNS with the domain name found in the address resolution step for the SRV records corresponding with the AVS service. There may be one or more SRV records for one or more AVS servers for redundancy and load sharing. It is the responsibility of the querying client to determine when to query an alternate AVS in the event that the preferred server is out-of-service given the stringent user interface latency requirements. It is expected that multiple algorithms will be explored as part of this experiment. 6.2 Address Validation LDAP Query The query to the address validation server of the recipient is made to find the spoken name of the recipient, the status of the mailbox, the capabilities of the mailbox, and the possible existence of sub- mailboxes. The message sender initiates the query and requests information based on the inter-domain email address of the recipient as found in the address resolution step. While this query is inherently simple and LDAP may be seen as overkill, it is useful to leverage the deployment experience and security work done with LDAP. The RESCAP work within the IETF may provide an alternative approach, and if successful may replace this protocol. At this time, the use of the voice messaging LDAP schema as defined in [VPIMLDAP] is specified for use in this experiment. 7. Intra-domain Message Routing Service A common intra-domain message routing challenge is addressed with a common schema for voice message routing. The ARS directory step yields an inter-domain email address sufficient to deliver a message to a given service provider. The service provider must then route the message within their network to the appropriate platform. To facilitate maximum interoperability for the duration of this experiment, a common schema is defined in [VPIMROUTE]. This schema is based in part on the work of the LASER group. As that work is completed and standardized, it is expected to replace the limited schema defined in [VPIMROUTE]. Vaudreuil, Parsons Expires 5/1/00 [Page 9] Internet Draft VPIM Directory December 1, 1999 8. Security Considerations The following are known security issues taken into consideration in the definition of this directory service. 1) Service provider customer information is very sensitive, especially in this time of local phone competition. Service providers require the 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 disclose of data useful for telemarketing such as the textual name and disclose only information useful to the sender such as the recipients spoken name, a data element much harder to auto-process. 2) Registration of an OCN for another carrier may result in messages being mis-directed to the wrong carrier. As sub-delegations are implemented, the risk that one the phone numbers delegated to one enterprise may be mis-pointed at another will increase. 3) Service providers operate in a regulated environment where certian information about a subscriber must not be disclosed. Voice Messaging is subject to caller-ID blocking restrictions, restrictions enforced in the telephony network. No such protection is available on the Internet. The protection of this data is essential, but is up to the individual service providers to not disclose this information outside of their control. 9. References [MIMEDIR] F. Dawson, T. Howes, & M. Smith, "A MIME Content-Type for Directory Information", Work In Progress, , March 1998 [DNS1] Mockapetris, P., "Domain names - implementation and specification", RFC1035, Nov 1987. [DNS2] Mockapetris, P., "Domain names - concepts and facilities", RFC 1034, Nov 1987. [E164] CCITT Recommendation E.164 (1991), Telephone Network and ISDN Operation, Numbering, Routing and Mobile Service - Numbering Plan for the ISDN Era. [TPC1] Malamud, Carl, Rose, Marshall, "Principles of Operation for the TPC.INT Subdomain: Remote Printing -- Technical Procedures", RFC 1530, October 1993. [VPIM2] Vaudreuil, Greg, Parsons, Glen, "Voice Profile for Internet Mail, Version 2", RFC 2421, September 1998. [VPIMe164] Vaudreuil, Greg, "Voice Messaging Directory Service: Principles of Operation", work-in-progress. Vaudreuil, Parsons Expires 5/1/00 [Page 10] Internet Draft VPIM Directory December 1, 1999 [VPIMARS] Vaudreuil, Greg, "Voice Messaging Directory Service: DNS-based", work-in-progress. [VPIMLDAP] Vaudreuil, Greg, " Voice Messaging Directory Service: Address Validation Schema", work-in-progress. [SRV] Gulbrandsen, A., Vixie, P., "A DNS RR for specifying the location of services (DNS SRV)", RFC 2052, October 1996. 10. Acknowledgments This experimental directory builds upon the earlier work of Carl Malamud and Marshall Rose in thier TPC.INT remote printing experiment and the work lead by Anne Brown as part of the EMA voice messaging committee's directory effort. Bernhard Elliot working with the TMIA has provided most of the organizational impetus to get this project moving, a substantial task given the sometimes slow and bureaucratic nature of the voice mail business and regulatory environment. Dave Dudley and the Messaging Aliance (TMA) for thier early work in pioneering a shared directory service for voice messaging and their continuing efforts to apply those learnings to this effort. 11. Copyright Notice "Copyright (C) The Internet Society (1998). 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 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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." Vaudreuil, Parsons Expires 5/1/00 [Page 11] Internet Draft VPIM Directory December 1, 1999 12. Authors' Addresses Gregory M. Vaudreuil Lucent Technologies, Communications Application Group 17080 Dallas Parkway Dallas, TX 75248-1905 United States Phone/Fax: +1-972-733-2722 Email: GregV@Lucent.Com Vaudreuil, Parsons Expires 5/1/00 [Page 12]