SIPPING Working Group J. Bakker, Ed. Internet-Draft Research In Motion (RIM) Intended status: Experimental December 2, 2011 Expires: June 4, 2012 Specification of 3GPP IM CN Subsystem XML body handling draft-bakker-sipping-3gpp-ims-xml-body-handling-07 Abstract This document registers new disposition-types for the Content- Disposition header field that apply to the application/3gpp-ims+xml body used by 3GPP. The applicability of these content-disposition values are limited to 3GPP IMS. The application/3gpp-ims+xml body has the following three distinct uses: (1) for redirecting the emergency session to use a different domain (e.g. using a Circuit Switched call), (2) for delivering user profile specific information from the SIP registrar to an Application Server, and (3) for causing a UAC to attempt to re-register with the IMS. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on June 4, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Bakker Expires June 4, 2012 [Page 1] Internet-Draft 3GPP IM CN Subsystem XML body handling December 2011 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. 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 field . . . . . . . . . . . . . . . 4 4.1. The application/3gpp-ims+xml MIME type with content disposition 3gpp-alternative-service . . . . . . . . . . . 4 4.2. Example application/3gpp-ims+xml MIME body with type XML element set to emergency . . . . . . . . . . . . . . . 4 4.3. The application/3gpp-ims+xml MIME type with content disposition 3gpp-service-info . . . . . . . . . . . . . . . 5 4.3.1. Example application/3gpp-ims+xml body . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . . 6 Appendix A. Revision Information . . . . . . . . . . . . . . . . . 6 A.1. version 00 . . . . . . . . . . . . . . . . . . . . . . . . 6 A.2. version 01 . . . . . . . . . . . . . . . . . . . . . . . . 7 A.3. version 02 . . . . . . . . . . . . . . . . . . . . . . . . 7 A.4. version 03 . . . . . . . . . . . . . . . . . . . . . . . . 7 A.5. version 04 . . . . . . . . . . . . . . . . . . . . . . . . 7 A.6. version 05 . . . . . . . . . . . . . . . . . . . . . . . . 7 A.7. version 06 . . . . . . . . . . . . . . . . . . . . . . . . 7 A.8. version 06 . . . . . . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Bakker Expires June 4, 2012 [Page 2] Internet-Draft 3GPP IM CN Subsystem XML body handling December 2011 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 field 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 field: 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 [5]. 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 [2]. The term "Application Server" (AS) is 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 [3] or a back-to-back UA (B2BUA) as defined in [3] based on the functions it needs to perform. There can be one or more ASes involved in a SIP session. Bakker Expires June 4, 2012 [Page 3] Internet-Draft 3GPP IM CN Subsystem XML body handling December 2011 4. Background for the new disposition-types for the Content-Disposition header field 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 network) or using another registration context, if a type XML element in the MIME body is set to "emergency". Section 21.3.5 of [3] specifies that, for the SIP 380 (Alternative Service) response, alternative services are described in the message body of the response. In IMS, for the purpose of indicating alternative domains, a SIP 380 (Alternative Service) response will include a MIME body and a Content-Type header field set to "application/3gpp-ims+xml". It is further possible that one or more UASes in the network experience service interuptions, e.g. when forwarding a (non- emergency) service request from a UAC. For example, there is no response to the service request and its retransmissions, a 3xx response or a 480 (Temporarily Unavailable) response is received for the request, the UAS does not have a needed user profile (e.g. due to restart or the UAS) and the attempt to retrieve the user profile fails. The UAS then responds with a 504 (Server Time-out), including a MIME body and a Content-Type header field set to "application/ 3gpp-ims+xml". Upon receiving the response, the UAC then creates another registration context in an attempt to restore the services, if a type XML element in the MIME body is set to "restoration". 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. 4.2. Example application/3gpp-ims+xml MIME body with type XML element set to emergency Bakker Expires June 4, 2012 [Page 4] Internet-Draft 3GPP IM CN Subsystem XML body handling December 2011 emergency 4.3. 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 AS. The SIP registrar downloads User Profile information and can transparently transfer User Profile specific information to the AS 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. 4.3.1. Example application/3gpp-ims+xml body 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) [4] 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 field that apply to the "application/3gpp-ims+xml" body used by 3GPP and are to be registered in the IANA registry for Mail Content Disposition Values and Parameters: Bakker Expires June 4, 2012 [Page 5] Internet-Draft 3GPP IM CN Subsystem XML body handling December 2011 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, Victor Pascual Avila, Christopher Wong for their guidance and comments that contributed to the progression of this work. 8. References 8.1. Normative 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] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] 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. [4] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. 8.2. Informative References [5] 3GPP, "IP Multimedia Call Control Protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 (Release 8)", 3GPP TS 24.229 V8.8.0, June 2009. Appendix A. Revision Information A.1. version 00 1. 2008-02-12, Initial version Bakker Expires June 4, 2012 [Page 6] Internet-Draft 3GPP IM CN Subsystem XML body handling December 2011 A.2. version 01 1. 2008-07-02, Updated reference and further aligned 3GPP TS 24.229 and this document A.3. version 02 1. 2009-03-01, Corrected "header" into "header field" A.4. version 03 1. 2010-02-23, no changes 2. 2011-02-09, no changes A.5. version 04 1. 2010-09-28, Introduces the case of addressing the MIME body's use for indicating the need to re-register with the IMS 2. 2010-09-28, Updates the reference to 3GPP TS 24.229 3. 2010-09-28, Introduces a reference to draft-patel-ecrit-sos-parameter-10 A.6. version 05 1. 2011-02-09, Editorially correct "registeration context" into "registration context" 2. 2011-02-09, Removed the reference to draft-patel-ecrit-sos-parameter-10 A.7. version 06 1. 2011-02-21, corrected, and changed, XML element name from "3gpp- ims" to "ims-3gpp" 2. 2011-02-21, Updated address information of author A.8. version 06 1. 2011-12-02, Updated address information of author Author's Address John-Luc Bakker (editor) Research In Motion (RIM) 5000 Riverside Drive, building 6, suite 100 Irving, Texas 75039 USA Phone: unlisted Fax: unlisted Email: jbakker@rim.com Bakker Expires June 4, 2012 [Page 7]