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Bakker, Ed. 3 Internet-Draft Research In Motion (RIM) 4 Intended status: Experimental March 27, 2012 5 Expires: September 28, 2012 7 Specification of 3GPP IM CN Subsystem XML body handling 8 draft-bakker-sipping-3gpp-ims-xml-body-handling-08 10 Abstract 12 This document registers new disposition-types for the Content- 13 Disposition header field that apply to the application/3gpp-ims+xml 14 body (part) used by 3GPP. The applicability of these content- 15 disposition values are limited to 3GPP IMS. The application/ 16 3gpp-ims+xml body (part) has the following three distinct uses: (1) 17 for redirecting the emergency session to use a different domain (e.g. 18 using a Circuit Switched call), (2) for delivering user profile 19 specific information from the SIP registrar to an Application Server, 20 and (3) for causing a UAC to attempt to re-register with the IMS. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on September 28, 2012. 39 Copyright Notice 41 Copyright (c) 2012 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Overall Applicability . . . . . . . . . . . . . . . . . . . . . 3 58 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 4. Background for the new disposition-types for the 63 Content-Disposition header field . . . . . . . . . . . . . . . 4 64 4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4 65 4.2. The application/3gpp-ims+xml MIME type with content 66 disposition 3gpp-alternative-service . . . . . . . . . . . 4 67 4.2.1. Example application/3gpp-ims+xml MIME body (part) 68 with type XML element set to emergency . . . . . . . . 5 69 4.3. The application/3gpp-ims+xml MIME type with content 70 disposition 3gpp-service-info . . . . . . . . . . . . . . . 5 71 4.3.1. Example application/3gpp-ims+xml body (part) . . . . . 5 73 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 75 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 77 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 79 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 80 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 81 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 83 Appendix A. Revision Information . . . . . . . . . . . . . . . . . 7 84 A.1. version 00 . . . . . . . . . . . . . . . . . . . . . . . . 7 85 A.2. version 01 . . . . . . . . . . . . . . . . . . . . . . . . 7 86 A.3. version 02 . . . . . . . . . . . . . . . . . . . . . . . . 7 87 A.4. version 03 . . . . . . . . . . . . . . . . . . . . . . . . 7 88 A.5. version 04 . . . . . . . . . . . . . . . . . . . . . . . . 7 89 A.6. version 05 . . . . . . . . . . . . . . . . . . . . . . . . 7 90 A.7. version 06 . . . . . . . . . . . . . . . . . . . . . . . . 7 91 A.8. version 07 . . . . . . . . . . . . . . . . . . . . . . . . 7 92 A.9. version 08 . . . . . . . . . . . . . . . . . . . . . . . . 8 94 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 96 1. Overall Applicability 98 This document makes certain assumptions regarding network topology 99 and the existence of transitive trust. These assumptions are 100 generally NOT APPLICABLE in the Internet as a whole. The mechanism 101 specified here was designed to satisfy the requirements specified by 102 the 3rd Generation Partnership Project for IP multimedia subsystem 103 (IMS) for which either no general-purpose solution was found, where 104 insufficient operational experience was available to understand if a 105 general solution is needed, or where a more general solution is not 106 yet mature. 108 2. Introduction 110 New disposition-types for the Content-Disposition header field can 111 only be registered with IANA according to procedures defined in 112 Section 9 of [1]. 114 The 3rd Generation Partnership Project (3GPP) (http://www.3gpp.org) 115 is specifying the IP multimedia subsystem (IMS) where SIP is the 116 protocol used to establish media sessions across different 117 participants. 119 This document registers new disposition-types for the Content- 120 Disposition header field: 3gpp-alternative-service and 3gpp-service- 121 info, to address specific requirements of the IMS. The new 122 disposition-types may not be applicable to the general Internet. The 123 new disposition types are applicable to the "application/ 124 3gpp-ims+xml" MIME type [5]. 126 3. Terminology 128 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 129 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 130 document are to be interpreted as described in [2]. 132 The term "Application Server" (AS) is introduced in this document. 134 An "Application Server" as referred to here is a SIP network server 135 that performs network based functions. The AS can act as a SIP Proxy 136 as defined in [3] or a back-to-back UA (B2BUA) as defined in [3] 137 based on the functions it needs to perform. There can be one or more 138 ASes involved in a SIP session. 140 4. Background for the new disposition-types for the Content-Disposition 141 header field 143 4.1. Introduction 145 Section 20.11 of [3] specifies that the Content-Disposition header 146 field describes how the message body or, for multipart messages, a 147 message body part is to be interpreted by the UAC or UAS. In 148 addition, [3] specifies that if this header field is missing, the 149 MIME type determines the default content disposition. If there is 150 none, "render" is assumed. 152 No default default content disposition has been defined for MIME type 153 "application/3gpp-ims+xml" MIME type. Sections 2.2 and 2.3 show how 154 a body (part) according to the MIME type is to be intepreted by 155 different entities (UE and AS) in 3GPP IMS. The difference in 156 requirements for UE and AS, coupled with the fact that the Content- 157 Disposition header field describes how the message body (part) is to 158 be interpreted, implies that a single default content disposition 159 value does not cover both cases 161 4.2. The application/3gpp-ims+xml MIME type with content disposition 162 3gpp-alternative-service 164 In the IMS it is possible that a UA attempts to place an emergency 165 call when the IMS network does not support emergency services. The 166 edge proxy detects the emergency call and can redirect the UE using a 167 SIP 380 (Alternative Service) to place the emergency call using 168 another domain (e.g. using a Circuit Switched network) or using 169 another registration context, if a type XML element in the MIME body 170 (part) is set to "emergency". 172 Section 21.3.5 of [3] specifies that, for the SIP 380 (Alternative 173 Service) response, alternative services are described in the message 174 body (part) of the response. In IMS, for the purpose of indicating 175 alternative domains, a SIP 380 (Alternative Service) response will 176 include a MIME body (part) and a Content-Type header field set to 177 "application/3gpp-ims+xml". 179 It is further possible that one or more UASes in the network 180 experience service interuptions, e.g. when forwarding a (non- 181 emergency) service request from a UAC. For example, there is no 182 response to the service request and its retransmissions, a 3xx 183 response or a 480 (Temporarily Unavailable) response is received for 184 the request, the UAS does not have a needed user profile (e.g. due to 185 restart or the UAS) and the attempt to retrieve the user profile 186 fails. The UAS then responds with a 504 (Server Time-out), including 187 a MIME body (part) and a Content-Type header field set to 188 "application/3gpp-ims+xml". Upon receiving the response, the UAC 189 then creates another registration context in an attempt to restore 190 the services, if a type XML element in the MIME body (part) is set to 191 "restoration". 193 Such configurations are generally not applicable to the internet as a 194 whole where such trust relationships do not exist. 196 In addition security issues have only been considered for networks 197 which are trusted and use hop by hop security mechanisms with 198 transitive trust and security issues with usage of this mechanism in 199 the general internet have not been evaluated. 201 4.2.1. Example application/3gpp-ims+xml MIME body (part) with type XML 202 element set to emergency 204 205 206 emergency 207 208 209 211 4.3. The application/3gpp-ims+xml MIME type with content disposition 212 3gpp-service-info 214 In 3GPP IMS the SIP registrar (S-CSCF) can perform a third party 215 registration to an AS. The SIP registrar downloads User Profile 216 information and can transparently transfer User Profile specific 217 information to the AS using a body (part) of MIME type "application/ 218 3gpp-ims+xml" in a SIP REGISTER request. In the example in Section 219 4.3.1, an International Mobile Subscriber Identity (IMSI) is 220 transferred. 222 4.3.1. Example application/3gpp-ims+xml body (part) 224 225 226 262013564857956 227 228 230 5. Security Considerations 232 It is necessary to protect the messages between proxies; 233 implementation SHOULD use a transport that provides integrity and 234 confidentially between the signaling hops. The Transport Layer 235 Security (TLS) [4] based signaling in SIP can be used to provide this 236 protection. 238 Security issues have only been considered for networks which are 239 trusted and use hop by hop security mechanisms with transitive trust 240 and security issues with usage of this mechanism in the general 241 internet have not been evaluated. 243 6. IANA Considerations 245 This document registers new disposition-types for the Content- 246 Disposition header field that apply to the "application/3gpp-ims+xml" 247 body (part) used by 3GPP and are to be registered in the IANA 248 registry for Mail Content Disposition Values and Parameters: 250 o 3gpp-alternative-service: the body (part) contains 3GPP IM CN 251 subsystem XML with the 'alternative-service' XML element as 252 described in Section 4.2; and 254 o 3gpp-service-info: the body (part) contains 3GPP IM CN subsystem 255 XML with the 'service-info' XML element as described in Section 256 4.3. 258 7. Acknowledgements 260 The author would like to thank Andrew Allen, Dean Willis, Cullen 261 Jennings, Victor Pascual Avila, Christopher Wong, Gonzalo Camarillo 262 and Paul Kyzivat for their guidance and comments that contributed to 263 the progression of this work. 265 8. References 267 8.1. Normative References 269 [1] Troost, R., Dorner, S., and K. Moore, "Communicating 270 Presentation Information in Internet Messages: The Content- 271 Disposition Header Field", RFC 2183, August 1997. 273 [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement 274 Levels", BCP 14, RFC 2119, March 1997. 276 [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 277 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 278 Session Initiation Protocol", RFC 3261, June 2002. 280 [4] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) 281 Protocol Version 1.1", RFC 4346, April 2006. 283 8.2. Informative References 285 [5] 3GPP, "IP Multimedia Call Control Protocol based on Session 286 Initiation Protocol (SIP) and Session Description Protocol 287 (SDP); Stage 3 (Release 8)", 3GPP TS 24.229 V8.8.0, June 2009. 289 Appendix A. Revision Information 291 A.1. version 00 292 1. 2008-02-12, Initial version 294 A.2. version 01 295 1. 2008-07-02, Updated reference and further aligned 3GPP TS 24.229 296 and this document 298 A.3. version 02 299 1. 2009-03-01, Corrected "header" into "header field" 301 A.4. version 03 302 1. 2010-02-23, no changes 303 2. 2011-02-09, no changes 305 A.5. version 04 306 1. 2010-09-28, Introduces the case of addressing the MIME body's use 307 for indicating the need to re-register with the IMS 308 2. 2010-09-28, Updates the reference to 3GPP TS 24.229 309 3. 2010-09-28, Introduces a reference to 310 draft-patel-ecrit-sos-parameter-10 312 A.6. version 05 313 1. 2011-02-09, Editorially correct "registeration context" into 314 "registration context" 315 2. 2011-02-09, Removed the reference to 316 draft-patel-ecrit-sos-parameter-10 318 A.7. version 06 319 1. 2011-02-21, corrected, and changed, XML element name from "3gpp- 320 ims" to "ims-3gpp" 321 2. 2011-02-21, Updated address information of author 323 A.8. version 07 324 1. 2011-12-02, Updated address information of author 326 A.9. version 08 327 1. 2012-27-03, Added a new background section 2.1 and renumbered 328 existing sections 329 2. 2012-27-03, Improved body handling text to not preclude multipart 330 bodies 331 3. 2012-27-03, Editorials 333 Author's Address 335 John-Luc Bakker (editor) 336 Research In Motion (RIM) 337 5000 Riverside Drive, building 6, suite 100 338 Irving, Texas 75039 339 USA 341 Phone: unlisted 342 Fax: unlisted 343 Email: jbakker@rim.com