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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 4, 2012) is 4214 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4346 (ref. '4') (Obsoleted by RFC 5246) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DISPATCH Working Group J. Bakker, Ed. 3 Internet-Draft Research In Motion (RIM) 4 Intended status: Standards Track September 4, 2012 5 Expires: March 8, 2013 7 Specification of 3GPP IM CN Subsystem XML body handling 8 draft-bakker-dispatch-3gpp-ims-xml-body-handling-00 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 [5]. The applicability of these content- 15 disposition values are limited to 3GPP IMS [5]. 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 March 8, 2013. 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. General . . . . . . . . . . . . . . . . . . . . . . . . 4 68 4.2.2. Example application/3gpp-ims+xml MIME body (part) 69 with type XML element set to emergency . . . . . . . . 5 70 4.3. The application/3gpp-ims+xml MIME type with content 71 disposition 3gpp-service-info . . . . . . . . . . . . . . . 5 72 4.3.1. General . . . . . . . . . . . . . . . . . . . . . . . . 5 73 4.3.2. Example application/3gpp-ims+xml body (part) . . . . . 6 75 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 77 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 81 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 82 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 83 8.2. Informative References . . . . . . . . . . . . . . . . . . 7 85 Appendix A. Revision Information . . . . . . . . . . . . . . . . . 7 86 A.1. version 00 . . . . . . . . . . . . . . . . . . . . . . . . 7 88 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 90 1. Overall Applicability 92 This document makes certain assumptions regarding network topology 93 and the existence of transitive trust. These assumptions are 94 generally NOT APPLICABLE in the Internet as a whole. The mechanism 95 specified here was designed to satisfy the requirements specified by 96 the 3rd Generation Partnership Project (3GPP) for IP multimedia 97 subsystem (IMS) for which either no general-purpose solution was 98 found, where insufficient operational experience was available to 99 understand if a general solution is needed, or where a more general 100 solution is not yet mature. 102 2. Introduction 104 New disposition-types for the Content-Disposition header field can 105 only be registered with IANA according to procedures defined in 106 Section 9 of [1]. 108 The 3rd Generation Partnership Project (3GPP) (http://www.3gpp.org) 109 is specifying the IP multimedia subsystem (IMS) [6] where SIP is the 110 protocol used to establish media sessions across different 111 participants. 113 This document registers new disposition-types for the Content- 114 Disposition header field: 3gpp-alternative-service and 3gpp-service- 115 info, to address specific requirements of the IMS. The new 116 disposition-types may not be applicable to the general Internet. The 117 new disposition types are applicable to the "application/ 118 3gpp-ims+xml" MIME type [5]. 120 3. Terminology 122 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 123 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 124 document are to be interpreted as described in [2]. 126 The term "Application Server" (AS) is introduced in this document. 128 An "Application Server" as referred to here is a SIP network server 129 that performs network based functions. The AS can act as a SIP Proxy 130 as defined in [3] or a back-to-back UA (B2BUA) as defined in [3] 131 based on the functions it needs to perform. There can be one or more 132 ASes involved in a SIP session. 134 4. Background for the new disposition-types for the Content-Disposition 135 header field 137 4.1. Introduction 139 Section 20.11 of [3] specifies that the Content-Disposition header 140 field describes how the message body or, for multipart messages, a 141 message body part is interpreted by the UAC or UAS. In addition, [3] 142 specifies that if this header field is missing, the MIME type 143 determines the default content disposition. If there is none, 144 "render" is assumed. 146 No default content disposition has been defined for MIME type 147 "application/3gpp-ims+xml" MIME type [5]. Sections 4.2 and 4.3 below 148 show how a body (part) according to the MIME type is interpreted by 149 different entities (UE and AS) in 3GPP IMS (each entity having a 150 different content handler for the same MIME media type tag). The 151 difference in requirements for UE and AS, coupled with the fact that 152 the Content-Disposition header field describes how the message body 153 (part) is interpreted, implies that a single default content 154 disposition value does not cover both cases. 156 NOTE: An alternative with a more general applicable approach could 157 e.g. be unique MIME media type tags, each associated with a 158 content handler. However, having unique MIME media type tags 159 at this stage raises backwards compatibility concerns for the 160 IP multimedia subsystem (IMS) [6]. 162 4.2. The application/3gpp-ims+xml MIME type with content disposition 163 3gpp-alternative-service 165 4.2.1. General 167 In the IMS it is possible that a UA attempts to place an emergency 168 call when the IMS network does not support emergency services. The 169 edge proxy can detect the emergency call and redirect the UE using a 170 SIP 380 (Alternative Service) to place the emergency call using 171 another domain (e.g. using a Circuit Switched network) or using 172 another registration context, if a type XML element in the MIME body 173 (part) is set to "emergency". 175 Section 21.3.5 of [3] specifies that, for the SIP 380 (Alternative 176 Service) response, alternative services are described in the message 177 body (part) of the response. In IMS, for the purpose of indicating 178 alternative domains, a SIP 380 (Alternative Service) response will 179 include a MIME body (part) and a Content-Type header field set to 180 "application/3gpp-ims+xml". 182 It is further possible that one or more UASes in the network 183 experience service interruptions, e.g. when forwarding a (non- 184 emergency) service request from a UAC. Examples of this are when 185 there is no response to the service request and its retransmissions, 186 a 3xx response or a 480 (Temporarily Unavailable) response is 187 received for the request, the UAS does not have a needed user profile 188 (e.g. due to restart of the UAS) and the attempt to retrieve the user 189 profile fails. In such situations the UAS responds with a 504 190 (Server Time-out), including a MIME body (part) and a Content-Type 191 header field set to "application/3gpp-ims+xml". Upon receiving this 192 response, the UAC can create another registration context in an 193 attempt to restore the services, if a type XML element in the MIME 194 body (part) is set to "restoration". 196 Such configurations are generally not applicable to the internet as a 197 whole where such trust relationships do not exist. 199 In addition, security issues have only been considered for networks 200 which are trusted and use hop by hop security mechanisms with 201 transitive trust. Security issues with usage of this mechanism in 202 the general internet have not been evaluated. 204 4.2.2. Example application/3gpp-ims+xml MIME body (part) with type XML 205 element set to emergency 207 208 209 emergency 210 211 212 214 4.3. The application/3gpp-ims+xml MIME type with content disposition 215 3gpp-service-info 217 4.3.1. General 219 In 3GPP IMS the SIP registrar (S-CSCF) can perform a third party 220 registration to an AS. The SIP registrar downloads User Profile 221 information and can transparently transfer User Profile specific 222 information to the AS using a body (part) of MIME type "application/ 223 3gpp-ims+xml" in a SIP REGISTER request. In the example in Section 224 4.3.2, an International Mobile Subscriber Identity (IMSI) is 225 transferred. 227 4.3.2. Example application/3gpp-ims+xml body (part) 229 230 231 262013564857956 232 233 235 5. Security Considerations 237 It is necessary to protect the messages between proxies; 238 implementation SHOULD use a transport that provides integrity and 239 confidentially between the signaling hops. The Transport Layer 240 Security (TLS) [4] based signaling in SIP can be used to provide this 241 protection. 243 Security issues have only been considered for networks which are 244 trusted and use hop by hop security mechanisms with transitive trust 245 and security issues with usage of this mechanism in the general 246 internet have not been evaluated. 248 6. IANA Considerations 250 This document registers new disposition-types for the Content- 251 Disposition header field that apply to the "application/3gpp-ims+xml" 252 body (part) used by 3GPP and are to be registered in the IANA 253 registry for Mail Content Disposition Values and Parameters: 255 o 3gpp-alternative-service: the body (part) contains 3GPP IM CN 256 subsystem XML with the 'alternative-service' XML element as 257 described in Section 4.2; and 259 o 3gpp-service-info: the body (part) contains 3GPP IM CN subsystem 260 XML with the 'service-info' XML element as described in Section 261 4.3. 263 7. Acknowledgements 265 The author would like to thank Andrew Allen, Dean Willis, Cullen 266 Jennings, Victor Pascual Avila, Christopher Wong, Gonzalo Camarillo, 267 Paul Kyzivat, and Atle Monrad for their guidance and comments that 268 contributed to the progression of this work. 270 8. References 271 8.1. Normative References 273 [1] Troost, R., Dorner, S., and K. Moore, "Communicating 274 Presentation Information in Internet Messages: The Content- 275 Disposition Header Field", RFC 2183, August 1997. 277 [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement 278 Levels", BCP 14, RFC 2119, March 1997. 280 [3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 281 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 282 Session Initiation Protocol", RFC 3261, June 2002. 284 [4] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) 285 Protocol Version 1.1", RFC 4346, April 2006. 287 8.2. Informative References 289 [5] IANA, "Registry for Application Media Types". 291 [6] 3GPP, "IP Multimedia Call Control Protocol based on Session 292 Initiation Protocol (SIP) and Session Description Protocol 293 (SDP); Stage 3 (Release 8)", 3GPP TS 24.229 V8.20.0, June 2012. 295 Appendix A. Revision Information 297 A.1. version 00 298 1. Initial version for consideration by dispatch, based upon 299 draft-bakker-sipping-3gpp-ims-xml-body-handling-08 300 2. Changed references to section 2.2 and 2.3 into 4.2 and 4.3, 301 respectively. 302 3. Updated abstract and section 2 and section 4.1 to reflect 303 discussions on the list 304 4. Various editorial comments 306 Author's Address 308 John-Luc Bakker (editor) 309 Research In Motion (RIM) 310 5000 Riverside Drive, building 6, suite 100 311 Irving, Texas 75039 312 USA 314 Phone: unlisted 315 Fax: unlisted 316 Email: jbakker@rim.com