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2 Dispatch Working Group A. Allen, Ed.
3 Internet-Draft Blackberry
4 Intended status: Informational October 18, 2013
5 Expires: April 21, 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-11
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 April 21, 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-17 [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-17 [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-17 [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-17 [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 circuit switched domain as in this scenario the
221 IMEI is the only common means for identifying the circuit switched
222 call is from the same mobile device that was in the emergency session
223 in the packet switched domain.
225 5. User Agent Client Procedures
227 A UAC that has an IMEI as specified in 3GPP TS 23.003 [10] that is
228 registering with a 3GPP IMS network MUST include in the
229 "sip.instance" media feature tag the GSMA IMEI URN according to the
230 syntax specified in draft-montemurro-gsma-imei-urn-17 [2] when
231 performing the registration procedures specified in RFC 5626 [1] or
232 RFC 5627 [3] or any other procedure requiring the inclusion of the
233 "sip.instance" media feature tag. The UAC SHOULD NOT include the
234 optional "svn" parameter in the GSMA IMEI URN in the "sip.instance"
235 media feature tag, since the software version can change as a result
236 of upgrades to the device firmware which would create a new
237 instance-id. Any future non zero values of the "vers" parameter, or
238 the future definition of additional parameters for the GSMA IMEI URN
239 that are intended to be used as part of an instance-id will require
240 an update to be made to this RFC. The UAC MUST provide character-by-
241 character identical URNs in each registration according to RFC 5626
242 [1]. Hence, any optional or variable components of the URN (e.g.,
243 the "vers" parameter) MUST be presented with the same values and in
244 the same order in every registration as in the first registration.
246 A UAC MUST only use the GSMA IMEI URN as an instance-id when
247 registering with a 3GPP IMS network. When registering with a non-
248 3GPP IMS network a UAC SHOULD use a UUID as an instance-id as
249 specified in RFC 5626 [1].
251 A UAC MUST NOT include the "sip.instance" media feature tag
252 containing the GSMA IMEI URN in the Contact header field of non-
253 REGISTER requests except when the request is related to an emergency
254 session. Regulatory requirements can require the IMEI to be provided
255 to the Public Safety Answering Point (PSAP). Any future exceptions
256 to this prohibition require a RFC that addresses how privacy is not
257 violated by such a usage.
259 6. User Agent Server Procedures
261 A UAS MUST NOT include its "sip.instance" media feature tag
262 containing the GSMA IMEI URN in the Contact header field of responses
263 except when the response is related to an emergency session.
264 Regulatory requirements can require the IMEI to be provided to the
265 Public Safety Answering Point(PSAP). Any future exceptions to this
266 prohibition require a RFC that addresses how privacy is not violated
267 by such a usage.
269 7. 3GPP SIP Registrar Procedures
271 In 3GPP IMS when the SIP Registrar receives in the Contact header
272 field a "sip.instance" media feature tag containing the GSMA IMEI URN
273 according to the syntax specified in
274 draft-montemurro-gsma-imei-urn-17 [2] the SIP registrar follows the
275 procedures specified in RFC 5626 [1]. If the UA indicates that it
276 supports the extension in RFC 5627 [3] and the SIP Registrar
277 allocates a public GRUU according to the procedures specified in RFC
278 5627 [3] the instance-id MUST be obfuscated when creating the "gr"
279 parameter in order not to reveal the IMEI to other UAs when the
280 public GRUU is included in non-REGISTER requests and responses. 3GPP
281 TS 24.229 [8] subclause 5.4.7A.2 specifies the mechanism for
282 obfuscating the IMEI when creating the "gr" parameter.
284 8. IANA considerations
286 This document defines no items requiring action by IANA.
288 9. Security considerations
290 Because IMEIs like other formats of instance-ids can be loosely
291 correlated to a user, they need to be treated as any other personally
292 identifiable information. In particular, the "sip.instance" media
293 feature tag containing the GSMA IMEI URN MUST NOT be included in
294 requests or responses intended to convey any level of anonymity, as
295 this could violate the users privacy. RFC 5626 [1] states "One case
296 where a UA could prefer to omit the "sip.instance" media feature tag
297 is when it is making an anonymous request or some other privacy
298 concern requires that the UA not reveal its identity". The same
299 concerns apply when using the GSMA IMEI URN as an instance-id.
300 Publication of the GSMA IMEI URN to networks that the UA is not
301 attached to or the UA does not have a service relationship with is a
302 security breach and the "sip.instance" media feature tag MUST NOT be
303 forwarded by the service provider's network elements when forwarding
304 requests or responses towards the destination UA. Additionally, an
305 instance-id containing the GSMA IMEI URN identifies a mobile device
306 and not a user. The instance-id containing the GSMA IMEI URN MUST
307 NOT be used alone as an address for a user or as an identification
308 credential for a user. The GRUU mechanism specified in RFC 5627 [3]
309 provides a means to create URIs that address the user at a specific
310 device or User Agent.
312 In order to protect the "sip.instance" media feature tag containing
313 the GSMA IMEI URN from being tampered with, those REGISTER requests
314 containing the GSMA IMEI URN MUST be sent using a security mechanism
315 such as TLS (RFC 4346 [5]) or another security mechanism that
316 provides equivalent levels of protection.
318 10. Acknowledgements
320 The author would like to thank Paul Kyzivat, Dale Worley, Cullen
321 Jennings, Adam Roach, Keith Drage, Mary Barnes, Peter Leis, James Yu,
322 S. Moonesamy, Roni Even, and Tim Bray for reviewing this draft and
323 providing their comments.
325 11. References
327 11.1. Normative references
329 [1] Jennings, C., Mahy, R., and F. Audet, "Managing Client-
330 Initiated Connections in the Session Initiation Protocol
331 (SIP)", RFC 5626, October 2009.
333 [2] Montemurro, M., "A Uniform Resource Name Namespace For The GSM
334 Association (GSMA) and the International Mobile station
335 Equipment Identity(IMEI), work in progress", Internet
336 Draft draft-montemurro-gsma-imei-urn-17, October 2013.
338 [3] Rosenberg, J., "Obtaining and Using Globally Routable User
339 Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)",
340 RFC 5627, October 2009.
342 [4] Moats, R., "URN Syntax", RFC 2141, May 1997.
344 [5] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
345 Protocol Version 1.1", RFC 4346, April 2006.
347 [6] Leach, P., Mealling, M., and R. Salz, "A Universally Unique
348 IDentifier (UUID) URN Namespace", RFC 4122, July 2005.
350 [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement
351 Levels", BCP 14, RFC 2119, March 1997.
353 [8] 3GPP, "TS 24.229: IP multimedia call control protocol based on
354 Session Initiation Protocol (SIP) and Session Description
355 Protocol (SDP); Stage 3 (Release 8)", 3GPP 24.229,
356 September 2013,
357 .
359 [9] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
360 Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
362 Session Initiation Protocol", RFC 3261, June 2002.
364 11.2. Informative references
366 [10] 3GPP, "TS 23.003: Numbering, addressing and identification
367 (Release 8)", 3GPP 23.003, September 2013,
368 .
370 [11] GSMA Association, "IMEI Allocation and Approval Guidelines",
371 PRD TS.06 (DG06) version 6.0, July 2011, .
375 [12] 3GPP, "TS 24.237: Mobile radio interface Layer 3 specification;
376 Core network protocols; Stage 3 (Release 8)", 3GPP 24.237,
377 September 2013,
378 .
380 [13] 3GPP, "TS 24.292: IP Multimedia (IM) Core Network (CN)
381 subsystem Centralized Services (ICS); Stage 3 (Release 8)",
382 3GPP 24.292, June 2013,
383 .
385 Author's Address
387 Andrew Allen (editor)
388 Blackberry
389 1200 Sawgrass Corporate Parkway
390 Sunrise, Florida 33323
391 USA
393 Email: aallen@blackberry.com