SIPPING Working Group J. Bakker, Ed. Internet-Draft Research in Motion (RIM) Intended status: Experimental February 12, 2008 Expires: August 15, 2008 Specification of 3GPP IM CN Subsystem XML body handling draft-bakker-sipping-3gpp-ims-xml-body-handling-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 August 15, 2008. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document registers new disposition-types for the Content- Disposition header that apply to the application/3gpp-ims+xml body used by 3GPP, since Release 5. The applicability of these content- disposition values are limited to 3GPP IMS. The application/ 3gpp-ims+xml body has the following two distinct uses: (1) for redirecting the emergency session to use a different domain (e.g. using a Circuit Switched call), and (2) for delivering user profile specific information from the SIP registrar to an Application Server. Bakker Expires August 15, 2008 [Page 1] Internet-Draft 3GPP IM CN Subsystem XML body handling February 2008 Table of Contents 1. Overall Applicability . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Background for the new disposition-types for the Content-Disposition header . . . . . . . . . . . . . . . . . . 4 4.1. The application/3gpp-ims+xml MIME type with content disposition 3gpp-alternative-service . . . . . . . . . . . 4 4.1.1. Example application/3gpp-ims+xml body . . . . . . . . . 5 4.2. The application/3gpp-ims+xml MIME type with content disposition 3gpp-service-info . . . . . . . . . . . . . . . 5 4.2.1. Example application/3gpp-ims+xml body . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Bakker Expires August 15, 2008 [Page 2] Internet-Draft 3GPP IM CN Subsystem XML body handling February 2008 1. Overall Applicability This document makes certain assumptions regarding network topology and the existence of transitive trust. These assumptions are generally NOT APPLICABLE in the Internet as a whole. The mechanism specified here was designed to satisfy the requirements specified by the 3rd Generation Partnership Project for IP multimedia subsystem (IMS) for which either no general-purpose solution was found, where insufficient operational experience was available to understand if a general solution is needed, or where a more general solution is not yet mature. 2. Introduction New disposition-types for the Content-Disposition header can only be registered with IANA according to procedures defined in Section 9 of [1]. The 3rd Generation Partnership Project (3GPP) (http://www.3gpp.org) is specifying the IP multimedia subsystem (IMS) where SIP is the protocol used to establish media sessions across different participants. This document registers new disposition-types for the Content- Disposition header: 3gpp-alternative-service and 3gpp-service-info, to address specific requirements of the IMS. The new disposition- types may not be applicable to the general Internet. The new disposition types are applicable to the application/3gpp-ims+xml MIME type [2]. 3. Terminology 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 [3]. The terms "Application Server" (AS), "Alternative Service", and "Service Info" are introduced in this document. An "Application Server" as referred to here is a SIP network server that performs network based functions. The AS can act as a SIP Proxy as defined in [4] or a back-to-back UA (B2BUA) as defined in [4] based on the functions it needs to perform. There can be one or more ASes involved in a SIP session. An "Alternative Service" is a MIME body included in a SIP 380 Bakker Expires August 15, 2008 [Page 3] Internet-Draft 3GPP IM CN Subsystem XML body handling February 2008 (Alternative Service) response with the Content-Type header value set to "application/3gpp-ims+xml", signalled from a SIP network server to SIP UAC, redirecting the emergency session to use different domain (e.g. using a Circuit Switched call). A "Service Info" is a MIME body included SIP request to an Application Server, with the Content-Type header value set to "application/3gpp-ims+xml" containing user profile specific data. Service Information is only included by the registrar in REGISTER requests where the registrar acts as a UAC [5]. 4. Background for the new disposition-types for the Content-Disposition header 4.1. The application/3gpp-ims+xml MIME type with content disposition 3gpp-alternative-service In the IMS it is possible that a UA attempts to place an emergency call when the IMS network does not support emergency services. The edge proxy detects the emergency call and can redirect the UE using a SIP 380 (Alternative Service) to place the emergency call using another domain (e.g. using a Circuit Switched call). Section 21.3.5 of [4] specifies that, for the SIP 380 (Alternative Service) response, alternative services are described in the message body of the response The application/3gpp-ims+xml MIME type with content disposition 3gpp- alternative-service is applicable in the following circumstances: o Where the invitee UA originates a SIP request containing in the R-URI a URI that identifies this request as an emergency session request; o The network also contains intermediate network SIP servers that are trusted; o The edge proxy has knowledge of the network's capability or policy to handle the requested (type of) emergency session. Such configurations are generally not applicable to the internet as a whole where such trust relationships do not exist. In addition security issues have only been considered for networks which are trusted and use hop by hop security mechanisms with transitive trust and security issues with usage of this mechanism in the general internet have not been evaluated. Bakker Expires August 15, 2008 [Page 4] Internet-Draft 3GPP IM CN Subsystem XML body handling February 2008 4.1.1. Example application/3gpp-ims+xml body <3gpp-ims version="1"> 4.2. The application/3gpp-ims+xml MIME type with content disposition 3gpp-service-info In 3GPP IMS the SIP registrar (S-CSCF) can perform a third party registration to an Application Server. The SIP registrar downloads User Profile information and can transparently transfer User Profile specific information to the Application Server using a body of MIME type application/3gpp-ims+xml in a SIP REGISTER request. In the example in Section 4.2.1, an International Mobile Subscriber Identity (IMSI) is transferred. 4.2.1. Example application/3gpp-ims+xml body <3gpp-ims version="1"> 262013564857956 5. Security Considerations It is necessary to protect the messages between proxies; implementation SHOULD use a transport that provides integrity and confidentially between the signaling hops. The Transport Layer Security (TLS) [6] based signaling in SIP can be used to provide this protection. Security issues have only been considered for networks which are trusted and use hop by hop security mechanisms with transitive trust and security issues with usage of this mechanism in the general internet have not been evaluated. 6. IANA Considerations This document registers new disposition-types for the Content- Disposition header that apply to the application/3gpp-ims+xml body Bakker Expires August 15, 2008 [Page 5] Internet-Draft 3GPP IM CN Subsystem XML body handling February 2008 used by 3GPP and are to be registered in the IANA registry for Mail Content Disposition Values and Parameters: o 3gpp-alternative-service: the body contains 3GPP IM CN subsystem XML with the 'alternative-service' XML element as described in Section 4.1; and o 3gpp-service-info: the body contains 3GPP IM CN subsystem XML with the 'service-info' XML element as described in Section 4.2. 7. Acknowledgements The author would like to thank Andrew Allen, Dean Willis, Cullen Jennings for their guidance and comments that contributed to the progression of this work. 8. References [1] Troost, R., Dorner, S., and K. Moore, "Communicating Presentation Information in Internet Messages: The Content- Disposition Header Field", RFC 2183, August 1997. [2] 3GPP, "IP Multimedia Call Control Protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 (Release 5)", 3GPP TS 24.229 V5.21.0, December 2007. [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [4] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [5] 3GPP, "IP Multimedia (IM) session handling; IM call model; Stage 2 (Release 5)", 3GPP TS 23.218 V5.9.0, June 2006. [6] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. Bakker Expires August 15, 2008 [Page 6] Internet-Draft 3GPP IM CN Subsystem XML body handling February 2008 Author's Address John-Luc Bakker (editor) Research in Motion (RIM) 5000 Riverside Drive, building 6, suite 100 Irving, Texas 75039 USA Email: jbakker@rim.com Bakker Expires August 15, 2008 [Page 7] Internet-Draft 3GPP IM CN Subsystem XML body handling February 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). Bakker Expires August 15, 2008 [Page 8]