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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Dispatch Working Group A. Allen, Ed. 3 Internet-Draft Blackberry 4 Intended status: Informational November 20, 2013 5 Expires: May 24, 2014 7 Using the International Mobile station Equipment Identity (IMEI) 8 Uniform Resource Name (URN) as an Instance ID 9 draft-allen-dispatch-imei-urn-as-instanceid-12 11 Abstract 13 This specification specifies how the Uniform Resource Name (URN) 14 reserved for the GSMA (GSM Association) identities and its sub- 15 namespace for the IMEI (International Mobile station Equipment 16 Identity) can be used as an instance-id. Its purpose is to fulfil 17 the requirements in RFC 5626 [1] that state "If a URN scheme other 18 than UUID (Universally unique identifier) is used, the UA (User 19 Agent) MUST only use URNs for which an RFC (from the IETF stream) 20 defines how the specific URN needs to be constructed and used in the 21 "+sip.instance" Contact header field parameter for outbound 22 behavior." 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on May 24, 2014. 41 Copyright Notice 43 Copyright (c) 2013 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 4. 3GPP Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 5 66 5. User Agent Client Procedures . . . . . . . . . . . . . . . . . 6 68 6. User Agent Server Procedures . . . . . . . . . . . . . . . . . 6 70 7. 3GPP SIP Registrar Procedures . . . . . . . . . . . . . . . . . 7 72 8. IANA considerations . . . . . . . . . . . . . . . . . . . . . . 7 74 9. Security considerations . . . . . . . . . . . . . . . . . . . . 7 76 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 78 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 79 11.1. Normative references . . . . . . . . . . . . . . . . . . . 8 80 11.2. Informative references . . . . . . . . . . . . . . . . . . 9 82 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 84 1. Introduction 86 This specification specifies how the Uniform Resource Name reserved 87 for GSMA identities and its sub-namespace for the IMEI (International 88 Mobile station Equipment Identity) as specified in 89 draft-montemurro-gsma-imei-urn-18 [2] can be used as an instance-id 90 as specified in RFC 5626 [1] and also as used by RFC 5627 [3]. 92 RFC 5626 [1] specifies the "+sip.instance" Contact header field 93 parameter that contains a URN as specified in RFC 2141 [4]. The 94 instance-id uniquely identifies a specific UA instance. This 95 instance-id is used as specified in RFC 5626 [1] so that the SIP 96 (Session Initiation Protocol) registrar (as specified in RFC 3261 97 [5]) can recognize that the contacts from multiple registrations 98 correspond to the same UA. The instance-id is also used as specified 99 by RFC 5627 [3] to create Globally Routable User Agent URIs (GRUUs) 100 that can be used to uniquely address a UA when multiple UAs are 101 registered with the same Address of Record (AoR). 103 RFC 5626 [1] requires that a UA SHOULD create a Universally Unique 104 Identifier (UUID) URN as specified in RFC 4122 [6] as its instance-id 105 but allows for the possibility to use other URN schemes. "If a URN 106 scheme other than UUID is used, the UA MUST only use URNs for which 107 an RFC (from the IETF stream) defines how the specific URN needs to 108 be constructed and used in the "+sip.instance" Contact header field 109 parameter for outbound behavior." This specification meets this 110 requirement by specifying how the GSMA IMEI URN is used in the 111 "+sip.instance" Contact header field parameter for outbound behavior, 112 and draft-montemurro-gsma-imei-urn-18 [2] specifies how the GSMA IMEI 113 URN is constructed. 115 The GSMA IMEI is a URN for the IMEI a globally unique identifier that 116 identifies mobile devices used in the Global System for Mobile 117 communications(GSM), Universal Mobile Telecommunications System 118 (UMTS) and 3GPP LTE (Long Term Evolution)networks. The IMEI 119 allocation is managed by the GSMA to ensure that the IMEI values are 120 globally unique. Details of the formatting of the IMEI as a URN are 121 specified in draft-montemurro-gsma-imei-urn-18 [2] and the definition 122 of the IMEI is contained in 3GPP TS 23.003 [10]. Further details 123 about the GSMA role in allocating the IMEI and the IMEI allocation 124 guidelines can be found in GSMA PRD TS.06 [11]. 126 2. 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 RFC 2119 [7]. 132 3. Background 134 GSM, UMTS and LTE capable mobile devices represent 90% of the mobile 135 devices in use worldwide. Every manufactured GSM, UMTS or LTE mobile 136 device has an allocated IMEI that uniquely identifies this specific 137 mobile device. Amongst other things in some regulatory jurisdictions 138 the IMEI is used to identify that a stolen mobile device is being 139 used, to help to identify the subscription that is using it and to 140 prevent use of the mobile device. Whilst GSM was originally a 141 circuit switched system, enhancements such as GPRS (General Packet 142 Radio Service) and UMTS have added IP data capabilities which along 143 with the definition of the IP (Internet Protocol) Multimedia 144 Subsystem (IMS) have made SIP based calls and IP multimedia sessions 145 from mobile devices possible. 147 The latest enhancement known as LTE introduces even higher data rates 148 and dispenses with the circuit switched infrastructure completely. 149 This means that with LTE networks, voice calls will need to be 150 conducted using IP and IMS. However, the transition to all IP, SIP 151 based IMS networks worldwide will take a great many years and mobile 152 devices being mobile will need to operate in both IP/SIP/IMS mode and 153 circuit switched mode. This means that calls and sessions will need 154 to be handed over between IP/SIP/IMS mode and circuit switched mode 155 mid-call or mid-session. Also since many existing GSM and UMTS radio 156 access networks are unable to support IP/SIP/IMS based voice services 157 in a commercially acceptable manner, some sessions could have some 158 media types delivered via IP/IMS simultaneously with voice media 159 delivered via the circuit switched domain to the same mobile device. 160 To achieve this the mobile device is needs to be simultaneously 161 attached via both the IP/SIP/IMS domain and the circuit switched 162 domain. 164 To meet this need 3GPP has specified how to maintain session 165 continuity between the IP/SIP/IMS domain and the circuit switched 166 domain in 3GPP TS 24.237 [12] and how to access IMS hosted services 167 via both the IP/SIP/IMS domain and the circuit switched domain in 168 3GPP TS 24.292 [13]. 170 In order for the mobile device to access SIP/IMS services via the 171 circuit switched domain 3GPP has specified a MSC (Mobile Switching 172 Center) server enhanced for ICS (IMS centralized services) and a MSC 173 server enhanced for SR-VCC (Single Radio Voice Call Continuity) that 174 control mobile voice call setup over the circuit switched radio 175 access while establishing the corresponding voice session in the core 176 network using SIP/IMS. To enable this, the MSC server enhanced for 177 ICS or MSC server enhanced for SR-VCC, perform SIP registration on 178 behalf of the mobile device which is also simultaneously directly 179 registered with the IP/SIP/IMS domain. The only mobile device 180 identifier that is transportable using GSM/UMTS/LTE signaling is the 181 IMEI therefore the instance-id included by the MSC server enhanced 182 for ICS or the MSC server enhanced for SR-VCC when acting on behalf 183 of the mobile device, and the instance-id directly included by the 184 mobile device both need to be based on the IMEI. 186 Additionally in order to meet the above requirements, the same IMEI 187 that is obtained from the circuit switched signaling by the MSC 188 server needs to be obtainable from SIP signaling so that that it can 189 be determined that both the SIP signaling and circuit switched 190 signaling originate from the same mobile device. 192 3GPP TS 24.237 [12] and 3GPP TS 24.292 [13] already specify the use 193 of the URN namespace for the GSMA IMEI URN as specified in 194 draft-montemurro-gsma-imei-urn-18 [2] as the instance-id used by GSM/ 195 UMTS/LTE mobile devices, the MSC server enhanced for SR-VCC and the 196 MSC server enhanced for ICS, for SIP/IMS registrations and emergency 197 related SIP requests for these reasons. 199 4. 3GPP Use Cases 201 1. The mobile device includes its IMEI in the SIP REGISTER request 202 so that the SIP registrar can perform a check of the Equipment 203 Identity Register (EIR) to verify if this mobile device is allowed or 204 barred from accessing the network for non-emergency services (e.g., 205 because it has been stolen). If the mobile device is not allowed to 206 access the network for non-emergency services the SIP registrar can 207 reject the registration. Thus a barred mobile device is prevented 208 from accesssing the network for non-emergency services. 210 2. The mobile device includes its IMEI in SIP INVITE requests used 211 to establish emergency sessions. This is so that the PSAP (Public 212 Safety Answering Point) can obtain the IMEI of the mobile device for 213 identification purposes if required by regulations. 215 3. The inclusion by the mobile device of its IMEI in SIP INVITE 216 requests used to establish emergency sessions is also used in the 217 cases of unauthenticated emergency sessions to enable the network to 218 identify the mobile device. This is especially important if the 219 unauthenticated emergency session is handed over from the packet 220 switched domain to the circuit switched domain. In this scenario the 221 IMEI is the only identifier that is common to both domains that the 222 Emergency Access Transfer Function (EATF) in the network, that 223 coordinates the transfer between domains, can use to identify that 224 the circuit switched call is from the same mobile device that was in 225 the emergency session in the packet switched domain. 227 5. User Agent Client Procedures 229 A UAC that has an IMEI as specified in 3GPP TS 23.003 [10] that is 230 registering with a 3GPP IMS network MUST include in the 231 "sip.instance" media feature tag the GSMA IMEI URN according to the 232 syntax specified in draft-montemurro-gsma-imei-urn-18 [2] when 233 performing the registration procedures specified in RFC 5626 [1] or 234 RFC 5627 [3] or any other procedure requiring the inclusion of the 235 "sip.instance" media feature tag. The UAC SHOULD NOT include the 236 optional "svn" parameter in the GSMA IMEI URN in the "sip.instance" 237 media feature tag, since the software version can change as a result 238 of upgrades to the device firmware which would create a new 239 instance-id. Any future non zero values of the "vers" parameter, or 240 the future definition of additional parameters for the GSMA IMEI URN 241 that are intended to be used as part of an instance-id will require 242 an update to be made to this RFC. The UAC MUST provide character-by- 243 character identical URNs in each registration according to RFC 5626 244 [1]. Hence, any optional or variable components of the URN (e.g., 245 the "vers" parameter) MUST be presented with the same values and in 246 the same order in every registration as in the first registration. 248 A UAC MUST only use the GSMA IMEI URN as an instance-id when 249 registering with a 3GPP IMS network. When registering with a non- 250 3GPP IMS network a UAC SHOULD use a UUID as an instance-id as 251 specified in RFC 5626 [1]. 253 A UAC MUST NOT include the "sip.instance" media feature tag 254 containing the GSMA IMEI URN in the Contact header field of non- 255 REGISTER requests except when the request is related to an emergency 256 session. Regulatory requirements can require the IMEI to be provided 257 to the Public Safety Answering Point (PSAP). Any future exceptions 258 to this prohibition require a RFC that addresses how privacy is not 259 violated by such a usage. 261 6. User Agent Server Procedures 263 A UAS MUST NOT include its "sip.instance" media feature tag 264 containing the GSMA IMEI URN in the Contact header field of responses 265 except when the response is related to an emergency session. 266 Regulatory requirements can require the IMEI to be provided to the 267 Public Safety Answering Point(PSAP). Any future exceptions to this 268 prohibition require a RFC that addresses how privacy is not violated 269 by such a usage. 271 7. 3GPP SIP Registrar Procedures 273 In 3GPP IMS when the SIP Registrar receives in the Contact header 274 field a "sip.instance" media feature tag containing the GSMA IMEI URN 275 according to the syntax specified in 276 draft-montemurro-gsma-imei-urn-18 [2] the SIP registrar follows the 277 procedures specified in RFC 5626 [1]. If the UA indicates that it 278 supports the extension in RFC 5627 [3] and the SIP Registrar 279 allocates a public GRUU according to the procedures specified in RFC 280 5627 [3] the instance-id MUST be obfuscated when creating the "gr" 281 parameter in order not to reveal the IMEI to other UAs when the 282 public GRUU is included in non-REGISTER requests and responses. 3GPP 283 TS 24.229 [8] subclause 5.4.7A.2 specifies the mechanism for 284 obfuscating the IMEI when creating the "gr" parameter. 286 8. IANA considerations 288 This document defines no items requiring action by IANA. 290 9. Security considerations 292 Because IMEIs like other formats of instance-ids can be loosely 293 correlated to a user, they need to be treated as any other personally 294 identifiable information. In particular, the "sip.instance" media 295 feature tag containing the GSMA IMEI URN MUST NOT be included in 296 requests or responses intended to convey any level of anonymity, as 297 this could violate the users privacy. RFC 5626 [1] states "One case 298 where a UA could prefer to omit the "sip.instance" media feature tag 299 is when it is making an anonymous request or some other privacy 300 concern requires that the UA not reveal its identity". The same 301 concerns apply when using the GSMA IMEI URN as an instance-id. 302 Publication of the GSMA IMEI URN to networks that the UA is not 303 attached to or the UA does not have a service relationship with is a 304 security breach and the "sip.instance" media feature tag MUST NOT be 305 forwarded by the service provider's network elements when forwarding 306 requests or responses towards the destination UA. Additionally, an 307 instance-id containing the GSMA IMEI URN identifies a mobile device 308 and not a user. The instance-id containing the GSMA IMEI URN MUST 309 NOT be used alone as an address for a user or as an identification 310 credential for a user. The GRUU mechanism specified in RFC 5627 [3] 311 provides a means to create URIs that address the user at a specific 312 device or User Agent. 314 In order to protect the "sip.instance" media feature tag containing 315 the GSMA IMEI URN from being tampered with, those REGISTER requests 316 containing the GSMA IMEI URN MUST be sent using a security mechanism 317 such as TLS (RFC 4346 [5]) or another security mechanism that 318 provides equivalent levels of protection. 320 10. Acknowledgements 322 The author would like to thank Paul Kyzivat, Dale Worley, Cullen 323 Jennings, Adam Roach, Keith Drage, Mary Barnes, Peter Leis, James Yu, 324 S. Moonesamy, Roni Even, and Tim Bray for reviewing this draft and 325 providing their comments. 327 11. References 329 11.1. Normative references 331 [1] Jennings, C., Mahy, R., and F. Audet, "Managing Client- 332 Initiated Connections in the Session Initiation Protocol 333 (SIP)", RFC 5626, October 2009. 335 [2] Montemurro, M., "A Uniform Resource Name Namespace For The 336 Global System for Mobile communications Association (GSMA) and 337 the International Mobile station Equipment Identity(IMEI), work 338 in progress", Internet Draft draft-montemurro-gsma-imei-urn-18, 339 November 2013. 341 [3] Rosenberg, J., "Obtaining and Using Globally Routable User 342 Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)", 343 RFC 5627, October 2009. 345 [4] Moats, R., "URN Syntax", RFC 2141, May 1997. 347 [5] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) 348 Protocol Version 1.1", RFC 4346, April 2006. 350 [6] Leach, P., Mealling, M., and R. Salz, "A Universally Unique 351 IDentifier (UUID) URN Namespace", RFC 4122, July 2005. 353 [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement 354 Levels", BCP 14, RFC 2119, March 1997. 356 [8] 3GPP, "TS 24.229: IP multimedia call control protocol based on 357 Session Initiation Protocol (SIP) and Session Description 358 Protocol (SDP); Stage 3 (Release 8)", 3GPP 24.229, 359 September 2013, 360 . 362 [9] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., 363 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: 364 Session Initiation Protocol", RFC 3261, June 2002. 366 11.2. Informative references 368 [10] 3GPP, "TS 23.003: Numbering, addressing and identification 369 (Release 8)", 3GPP 23.003, September 2013, 370 . 372 [11] GSMA Association, "IMEI Allocation and Approval Guidelines", 373 PRD TS.06 (DG06) version 6.0, July 2011, . 377 [12] 3GPP, "TS 24.237: Mobile radio interface Layer 3 specification; 378 Core network protocols; Stage 3 (Release 8)", 3GPP 24.237, 379 September 2013, 380 . 382 [13] 3GPP, "TS 24.292: IP Multimedia (IM) Core Network (CN) 383 subsystem Centralized Services (ICS); Stage 3 (Release 8)", 384 3GPP 24.292, June 2013, 385 . 387 Author's Address 389 Andrew Allen (editor) 390 Blackberry 391 1200 Sawgrass Corporate Parkway 392 Sunrise, Florida 33323 393 USA 395 Email: aallen@blackberry.com