Internet Draft Greg Vaudreuil Expires in six months Lucent Technologies December 1, 1999 Voice Messaging Directory: Address Resolution Services 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 provides details of the address resolution service inter-domain message routing, and address validation server discovery of ane experimental voice messaging directory service. The service is described in [vpime164]. 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. OPERATIONAL GOALS AND CONSTRAINTS ...................................4 2.1Performance Goals .................................................4 2.2Scaling Goals .....................................................5 2.3Administrative / Operational goals ................................5 2.4Interoperability Goals ............................................5 3. ADDRESS RESOLUTION SERVICE ..........................................6 4. SECURITY CONSIDERATIONS .............................................6 5. REFERENCES ..........................................................7 6. ACKNOWLEDGMENTS .....................................................7 7. COPYRIGHT NOTICE ....................................................7 8. AUTHORS' ADDRESSES ..................................................8 Vaudreuil, Parsons Expires 5/1/00 [Page 3] Internet Draft VPIM Directory December 1, 1999 1. Abstract The telephone number delegation and call routing system is a hierarchitecal system. ITU standard E.164 defines the structure of the telephone number as follows: {country code) (Nationally significant part) The country code may be from one to three digits, and the total length may be up to 16 digits. The nationally significant portion may be arbitraily divided on any number boundary. In many countries numering plans, the divisions are not uniform, that is, the "area codes" or "City codes" may be of varying lengths within a single country and the total number of digits may be variable. Within this flexiblity, it is always the case that the delegation of authority is done left-to-right. With this assumption, a numbering tree can be built on a digit-by-digit basis can represent any of these hierarchical structures. DNS permits the delegation of authority on arbitary boundaries such that a delegation to country code "1", "44", and "972" can all coexist under a single numbering plan root. The same applies for "area codes", "City codes" or "service selectors" within numbering plans. The protocol mechanics outlined in this document are devised in such a manner that the clients do not need any knowledge of the numbering plan itself to correctly construct a query of the Address Resolution Service. The client may mechanically collect digits, format the query, and receive a response to any telephone number in the world. 2. Operational Goals and Constraints 2.1 Performance Goals The entire time budget for the address resolution query is 500 milliseconds. The telephone number hierarchy technically has a maximum depth of 16. In practice four levels are a practical maximum number of delegations. In DNS, each sub-delegation may require an additional chained or referred query. In a well connected and correctly functioning system, each query should take no more than 100ms. For the common case, caching of the country codes will typically reduce the total number of queries to one or two. With this, we believe the latency requirements are achievable. After resolving the address, the address validation server must be found. The time budget is 250ms. Retreival of a DNS record from a traditional domain name may require up to three lookups based on the depth of the the domain name delegation. Since the top-level lookup is effectively cached, two DNS queries are typically required. In practice, the number of destination networks to which message are sent is relatively small, so caching may further reduce the number of queries necessary. At 100ms two queries is just within the 250ms time budget. Vaudreuil, Parsons Expires 5/1/00 [Page 4] Internet Draft VPIM Directory December 1, 1999 2.2 Scaling Goals Without local number portability, it should not be necessary to provision each telephone number into the DNS. Within North America, the delegation of phone numbers to local exchange carriers is done on the 6th digit boundary. (Counter to common belief, the Area Code is not a delegation point). Today, the total number of number delegations under country code 1 is about 125K. This is within the number of subdomains that can be supported on a suitably resourced DNS server. For an NPA/NXX that is subject to number portability, each telephone number may be considered a separate sub-delegation. In the worst case, the total number of sub-delegations may reach a theoretical 10K. While it is not expected that this volatile data will be placed in a DNS zone file, it is at least technically possible. A more likely implementation would be a DNS interface into a relational database or service provider operational database. 2.3 Administrative / Operational goals The maintenance of the hierarchy needs to be as mechanical as possible. There is not yet a business case for managing the DNS sub- tree, so the total expense needs to be within the budget of some willing donor organization. The top-level delegations of country codes are public information. While the creation and destruction of nations is not uncommon, the data is relatively static. Delegations within North America are managed through the Local Routing Authority (LRA) which publishes a quarterly list of delegations called the Local Exchange Routing Guide (LERG). This guide is available by subscription from Telecordia, the LRA secretariat, for a nominal fee. Within North America, the mapping between the Operating Company Number (OCN) and a domain name is not currently available. This is expected to be relatively static mapping that will add entries as new service providers join the experimental directory service. Initially the total number is expected to be well under one hundred. The total number of operating companies is well under a thousand. This registration process is not expected to be excessively burdensome. Converting the LERG plus the domain to OCN mapping data into DNS zone files is a mechanical process that lends itself to scripting. This is not expected to incur substantial operational costs. 2.4 Interoperability Goals It is intended that this solution work with the common, deployed DNS resolver libraries in the most common operating systems. It is understood that application clients will have to be created that understand the specific "schema" for address resolution. Vaudreuil, Parsons Expires 5/1/00 [Page 5] Internet Draft VPIM Directory December 1, 1999 3. The Address Resolution Service The address resolution service loads the telephone number hierarchy into the domain name system. This is performed by splitting the telephone number into single-digit units and treating each digit as a DNS domain-label. The DNS is thus queried by converting the dialed telephone number into a domain name and using that domain name to query for a record from DNS. The ARS query simply requests the responsible domain for a given telephone number. This can most simply provided by using the widely deployed PTR record and applying it to this role. With the PTR, a query by a telephone number converted into a domain name form can return the domain name associated with it! Sub-delegations of the ARS can be achieved with the existing mechanism. (add description) The inter-domain VPIM email address is constructed by converting the dialed telephone number into international form and concatenating it with the domain name returned in the PTR record from the DNS query. Example: Configuration file for the NANP node in the DNS tree *.3.3.7.2.7.9 PTR Voice.SP.net (for 972 733) *.3.2.8.4.1.2 PTR Voice.SP.net (for 214 823) Example query using telephone number +1 972 733 2722 Query: 2.2.7.2.3.3.7.2.7.9.1.e164.int Result: PTR = voice.SP.net Resulting Inter-domain email address: +19727332722@voice.sp.net 4. Security Considerations The following are known security issues taken into consideration in the definition of this directory service. 1) Registration of a domain name for an OCN that belongs to another carrier may result in messages being mis-directed to the wrong carrier. 2) As sub-delegations are implemented, the risk that the phone numbers delegated to one enterprise may be mis-pointed at another will increase. Vaudreuil, Parsons Expires 5/1/00 [Page 6] Internet Draft VPIM Directory December 1, 1999 5. 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 6. 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. Bernard 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. 7. 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 Vaudreuil, Parsons Expires 5/1/00 [Page 7] Internet Draft VPIM Directory December 1, 1999 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." 8. 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 8]