Telephone Number Mapping R. Walter Internet Draft D. Ranalli Document: draft-walter-ranalli-enum-service-00.txt NetNumber, Inc. Category: Standards Track October, 2001 ENUM Resolution Protocols and Services Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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 draft documents 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 "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. Abstract This document describes a set of ENUM resolution protocols and services that enable communication applications to unambiguously differentiate between multiple communication services associated with a single E.164 telephone number. 1. Conventions used in this document 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 RFC-2119 [2]. 2. Introduction The ENUM protocol described in RFC 2916 [3] utilizes the Domain Name System (DNS) [4] to provide for the translation of E.164 domain names into protocol and service specific uniform resource identifiers or URI's [5]. ENUM enabled applications are responsible for determining if the results of an ENUM query contain protocol and service specific URI's that are relevant to the applications purpose. This is achieved by examining the resolution protocol and service(s) contained in the service field of the returned NAPTR resource records [6]. RFC 2916 defines a single resolution service named "E.164 to URI" (E2U). The E2U resolution service indicates to an application that Walter, et al. Expires April 26, 2002 [Page 1] Internet Draft ENUM Resolution Protocols and Services October 2001 the result of processing the NAPTR record is one or more URIs, but does not indicate the specific service associated with the URI(s). The application must infer the nature of the service by examining the resolution protocol, however this is ambiguous when there is more than one NAPTR RR containing the same resolution protocol. A simple example of this is when both a SIP based telephony service and a SIP based instant messaging service exist for the same telephone number. The example below highlights the ambiguity created by multiple NAPTR RRs with a common resolution protocol. In this scenario, an application cannot discern the SIP-based "telephony" service from the SIP-based "instant messaging" service. Similarly, an application cannot discern the SMTP-based "email" service from the SMTP-based "voicemail" service. 4.3.2.1.6.7.9.8.6.4 IN NAPTR 0 0 "u" "sip+E2U" "!^.*$!sip:4689761234@tele.fr!" . IN NAPTR 0 0 "u" "sip+E2U" "!^.*$!sip:pierre33@msn.com!" . IN NAPTR 0 0 "u" "smtp+E2U" "!^.*$!mailto:4689761234@tele.fr!" . IN NAPTR 0 0 "u" "smtp+E2U" "!^.*$!mailto:pierre33@hotmail.com!". Well defined, standardized resolution protocols and services are needed to enable communication applications to unambiguously differentiate between multiple services. There are many potential resolution protocol and services that may be associated with an E.164 telephone number. In order to facilitate the deployment of communications applications that work across multiple service provider and technology vendor environments, care must be taken to only specify resolution protocols and services for which there is wide acceptance. This document specifies an initial set of resolution protocols and services for telephony, electronic mail, voice messaging, instant messaging and presence applications. 3. Resolution Protocols The following ENUM resolution protocols MUST be used to identify the protocol associated with one or more of the resolution services defined in section 4. 3.1 Specification of Resolution Protocol - SIP This resolution protocol identifies that the resulting service uses Session Initiation Protocol (SIP) [7]. * Name: SIP - Session Initiation Protocol * Mnemonic: SIP Walter, et al. Expires April 26, 2002 [Page 2] Internet Draft ENUM Resolution Protocols and Services October 2001 3.2 Specification of Resolution Protocol - H323 This resolution protocol identifies that the resulting service uses H.323 protocols (H323) [8]. * Name: H.323 - IP Telephony Protocol(s) * Mnemonic: H323 3.3 Specification of Resolution Protocol - SMTP This resolution protocol identifies that the resulting service uses Simple Mail Transfer Protocol (SMTP) [9]. * Name: SMTP - Simple Mail Transfer Protocol * Mnemonic: SMTP 4. Resolution Services The following ENUM resolution services MUST be used to identify the services associated with an E.164 telephone number and URI. 4.1 Specification of Service - E2TEL This resolution service identifies the primary telephony service associated with an E.164 number. * Name: E.164 to Telephony Service URI * Mnemonic: E2TEL 4.2 Specification of Service - E2EM * Name: E.164 to Electronic Mail URI * Mnemonic: E2EM 4.3 Specification of Service - E2VM * Name: E.164 to Voice Messaging URI * Mnemonic: E2VM 4.4 Specification of Service - E2IM * Name: E.164 to Instant Messaging URI * Mnemonic: E2IM 4.5 Specification of Service - E2PRES * Name: E.164 to Presence URI * Mnemonic: E2PRES Walter, et al. Expires April 26, 2002 [Page 3] Internet Draft ENUM Resolution Protocols and Services October 2001 5. Examples The following examples illustrate how specific resolution protocols and services MAY be utilized to differentiate between applications that use common protocols. 5.1 SIP-based Telephony and Instant Messaging Services 4.3.2.1.6.7.9.8.6.4 IN NAPTR 0 0 "u" "sip+E2TEL" "!^.*$!sip:4689761234@tele.fr!" . IN NAPTR 0 0 "u" "sip+E2IM" "!^.*$!sip:pierre33@msn.com!" . 5.2 SMTP-based E-Mail and Voice Messaging Services 2.1.2.1.5.5.5.9.7.2.1 IN NAPTR 0 0 "u" "smtp+E2EM" "!^.*$!mailto:henry@mail.us!" . IN NAPTR 0 0 "u" "smtp+E2VM" "!^.*$!mailto:hsmith@company.com!" . 5.3 SIP-based Telephony and Instant Messaging Services Sharing a URI The following example illustrates two communications services associated with one E.164 telephone number, protocol and URI. 4.3.2.1.6.7.9.8.6.4 IN NAPTR 0 0 "u" "sip+E2TEL+E2IM" "!^.*$!sip:pierre33@msn.com!" . Note: The service field of the NAPTR is limited to 32 bytes. This should be sufficient as long as the single URI is associated with relatively few services. A less compact implementation of this example would be: 4.3.2.1.6.7.9.8.6.4 IN NAPTR 0 0 "u" "sip+E2TEL" "!^.*$!sip:pierre33@msn.com!" . IN NAPTR 0 0 "u" "sip+E2IM" "!^.*$!sip:pierre33@msn.com!" . 6. Security Considerations The use of resolution protocols and services does not introduce any new security considerations. 7. References [1] S. Bradner, "The Internet Standards Process -- Revision 3, BCP9," RFC 2026, October 1996. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] P. Faltstrom, "E.164 number and DNS," RFC 2916, September 2000. Walter, et al. Expires April 26, 2002 [Page 4] Internet Draft ENUM Resolution Protocols and Services October 2001 [4] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [5] Berners-Lee, T., Fielding, R.T. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [6] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS Resource Record", RFC 2915, September 2000. [7] Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg, "SIP: Session Initiation Protocol", RFC 2543, March 1999. [8] ITU, "Visual telephone systems and equipment for local area networks which provide a non-guaranteed quality of service", Recommendation H.323, Telecommunication Standardization Sector of ITU, Geneva, Switzerland, May 1996. [9] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, USC/Information Sciences Institute, August 1982. 8. Acknowledgments Thanks to Michael Mealling for his feedback on the intended use of resolution protocols and services. 9. Author Address Robert H. Walter NetNumber, Inc. 650 Suffolk Street Suite 307 Lowell, MA 01854 Phone: +1-978-848-2831 Email: rwalter@netnumber.com Douglas J. Ranalli NetNumber, Inc. 650 Suffolk Street Suite 307 Lowell, MA 01854 Phone: +1-978-848-2830 Email: dranalli@netnumber.com Walter, et al. Expires April 26, 2002 [Page 5] Internet Draft ENUM Resolution Protocols and Services October 2001 Full Copyright Statement "Copyright (C) The Internet Society (date). 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 implmentation 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. 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