ENUM -- Telephone Number Mapping O. Lendl Working Group enum.at Internet-Draft May 2, 2008 Expires: November 3, 2008 IANA Registration for the enumservice-subtype 'sip:lr' draft-lendl-enum-sip-lr-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on November 3, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document requests IANA registration of an enumservice-subtype for loose route variant for SIP, the Session Initiation Protocol. This subtype allows for the routing of SIP messages addressed to tel: Uniform Resource Identifiers (URIs) according to [I-D.rosenberg-sip-ua-loose-route]. Lendl Expires November 3, 2008 [Page 1] Internet-Draft SIP Loose Route Enumservice May 2008 Table of Contents 1. Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. ENUM Service Registration - sip:lr . . . . . . . . . . . . . . 4 4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Security & Privacy Considerations . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. DNS Considerations . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Lendl Expires November 3, 2008 [Page 2] Internet-Draft SIP Loose Route Enumservice May 2008 1. Preface There is discussion in the IETF SIP working group regarding the introduction of a distinction between "routing" and "retargeting" of SIP calls. No consensus has been reached yet. This document is based on one of the proposals ([I-D.rosenberg-sip-ua-loose-route]). The purpose of this I-D is to stimulate discussion in the ENUM WG on what the implications could be if the ua-loose-route idea is standardized. 2. Introduction E.164 Number Mapping (ENUM) [RFC3761] uses the Domain Name System (DNS) [RFC1035] to refer from E.164 numbers [refs.E164] to Uniform Resource Identifiers (URIs) [RFC3986]. Specific services to be used with ENUM must be registered with IANA. [I-D.ietf-enum-enumservices-guide] describes the process of such an Enumservice registration. The enumservice registration for SIP Addresses-of-Record [RFC3764] defines a mapping from E.164 telephone number to a SIP AoR which can be used by SIP devices to retarget a telephone number based call towards a SIP AoR. INVITE messages generated by this process use the retrieved AoR as the Request URI. If further call routing hops are done based on the original telephone number (TN), the ENUM entry often contains not a true AoR, but something like sip:TN@nexthop.example.com;user=phone. The SIP proxy at that next hop extracts the TN from the Request URI and applies his own TN-based routing algorithm to determine the next steps. According to [I-D.rosenberg-sip-ua-loose-route], this is a clear example of a "routing" operation and not a "retargetting" operation, as from a logical point of view the call is still addressed to the same telephone number. Consequently, the Request-URI should be kept, and only a Route header should be inserted to indicate the next SIP hop. For backward compatibility reasons, it is necessary (Section 6, last paragraph in [I-D.rosenberg-sip-ua-loose-route]) that the next hop indicates that he supports loose-route. This subtype for the "sip" enumservice does exactly that: it allows the destination network to announce that it supports loose routing as defined by [I-D.rosenberg-sip-ua-loose-route]. Lendl Expires November 3, 2008 [Page 3] Internet-Draft SIP Loose Route Enumservice May 2008 3. ENUM Service Registration - sip:lr The following template contains information required for the IANA registrations of the "lr" subtype for the Enumservice "sip", according to [I-D.ietf-enum-enumservices-guide]: Enumservice Type: "sip" Enumservice Subtype: "lr" URI Schemes: "sip" Functional Specification: This Enumservice/subtype indicates that the resource identified is a SIP next hop towards the endpoint identified by the telephone number as defined by [I-D.rosenberg-sip-ua-loose-route]. Security Considerations: see Section 5 Intended Usage: COMMON Registration Document: This document's RFC number once it is published. Author: Otmar Lendl 4. Example An example ENUM entry indicating a SIP next hop could look like: $ORIGIN 6.9.4.0.6.9.4.5.1.1.4.4.e164.arpa. @ IN NAPTR ( 100 10 "u" "E2U+sip:lr" "!^.*$!sip:p1.example.com;lr!" . ) To visualize the difference between how "sip" and "sip:lf" entries are interpreted, consider the following entries: $ORIGIN 6.9.4.0.6.9.4.5.1.1.4.4.e164.arpa. @ IN NAPTR ( 100 10 "u" "E2U+sip" "!^.*$!sip:alice@example.com!" . ) @ IN NAPTR ( 100 10 "u" "E2U+sip:lr" "!^.*$!sip:p1.example.com;lr!" . Lendl Expires November 3, 2008 [Page 4] Internet-Draft SIP Loose Route Enumservice May 2008 ) A SIP proxy dealing with a call to tel:+441154960496 can select either record. The first leads to INVITE sip:alice@example.com SIP/2.0 being sent to the proxy responsible for example.com. If the sip:lr record is used, then INVITE tel:+441154960496 SIP/2.0 Route: is sent to p1.example.com. 5. Security & Privacy Considerations The registration document of the "sip" enumservice ([RFC3764]) contains an extensive Security section. The loose route subtype adds no new concerns, to the contrary: as the SIP URI contained in such a records does not contain a (potentially revealing) AoR, but only a hostname and port, it is less likely to leak personal information. On the other hand, the hostnames contained in these records may expose information on the internal network topology. 6. IANA Considerations This memo requests IANA to add a new "lr" Enumservice subtype to the 'Enumservice Registrations' registry entry for "sip", according to the definitions in this document and [I-D.ietf-enum-enumservices-guide]. The required template is contained in Section 3. 7. DNS Considerations This is a straight forward ENUM service-type. 8. References Lendl Expires November 3, 2008 [Page 5] Internet-Draft SIP Loose Route Enumservice May 2008 8.1. Normative References [RFC3761] Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application (ENUM)", RFC 3761, April 2004. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC3764] Peterson, J., "enumservice registration for Session Initiation Protocol (SIP) Addresses-of-Record", RFC 3764, April 2004. [I-D.ietf-enum-enumservices-guide] Hoeneisen, B., Mayrhofer, A., and J. Livingood, "IANA Registration of Enumservices: Guide, Template and IANA Considerations", draft-ietf-enum-enumservices-guide-08 (work in progress), March 2008. 8.2. Informative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [refs.E164] ITU-T, "The international public telecommunication numbering plan", Recommendation E.164 (02/05), Feb 2005. [I-D.rosenberg-sip-ua-loose-route] Rosenberg, J., "Applying Loose Routing to Session Initiation Protocol (SIP) User Agents (UA)", draft-rosenberg-sip-ua-loose-route-02 (work in progress), January 2008. Author's Address Otmar Lendl enum.at GmbH Karlsplatz 1/9 Wien A-1010 Austria Phone: +43 1 5056416 33 Email: otmar.lendl@enum.at URI: http://www.enum.at/ Lendl Expires November 3, 2008 [Page 6] Internet-Draft SIP Loose Route Enumservice May 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Lendl Expires November 3, 2008 [Page 7]