Dispatch Working Group A. Allen, Ed. Internet-Draft Blackberry Intended status: Informational November 20, 2013 Expires: May 24, 2014 Using the International Mobile station Equipment Identity (IMEI) Uniform Resource Name (URN) as an Instance ID draft-allen-dispatch-imei-urn-as-instanceid-12 Abstract This specification specifies how the Uniform Resource Name (URN) reserved for the GSMA (GSM Association) identities and its sub- namespace for the IMEI (International Mobile station Equipment Identity) can be used as an instance-id. Its purpose is to fulfil the requirements in RFC 5626 [1] that state "If a URN scheme other than UUID (Universally unique identifier) is used, the UA (User Agent) MUST only use URNs for which an RFC (from the IETF stream) defines how the specific URN needs to be constructed and used in the "+sip.instance" Contact header field parameter for outbound behavior." 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 May 24, 2014. Copyright Notice Copyright (c) 2013 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 Allen Expires May 24, 2014 [Page 1] Internet-Draft Using IMEI URN as an Instance ID November 2013 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect 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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. 3GPP Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 5 5. User Agent Client Procedures . . . . . . . . . . . . . . . . . 6 6. User Agent Server Procedures . . . . . . . . . . . . . . . . . 6 7. 3GPP SIP Registrar Procedures . . . . . . . . . . . . . . . . . 7 8. IANA considerations . . . . . . . . . . . . . . . . . . . . . . 7 9. Security considerations . . . . . . . . . . . . . . . . . . . . 7 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 11.1. Normative references . . . . . . . . . . . . . . . . . . . 8 11.2. Informative references . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Allen Expires May 24, 2014 [Page 2] Internet-Draft Using IMEI URN as an Instance ID November 2013 1. Introduction This specification specifies how the Uniform Resource Name reserved for GSMA identities and its sub-namespace for the IMEI (International Mobile station Equipment Identity) as specified in draft-montemurro-gsma-imei-urn-18 [2] can be used as an instance-id as specified in RFC 5626 [1] and also as used by RFC 5627 [3]. RFC 5626 [1] specifies the "+sip.instance" Contact header field parameter that contains a URN as specified in RFC 2141 [4]. The instance-id uniquely identifies a specific UA instance. This instance-id is used as specified in RFC 5626 [1] so that the SIP (Session Initiation Protocol) registrar (as specified in RFC 3261 [5]) can recognize that the contacts from multiple registrations correspond to the same UA. The instance-id is also used as specified by RFC 5627 [3] to create Globally Routable User Agent URIs (GRUUs) that can be used to uniquely address a UA when multiple UAs are registered with the same Address of Record (AoR). RFC 5626 [1] requires that a UA SHOULD create a Universally Unique Identifier (UUID) URN as specified in RFC 4122 [6] as its instance-id but allows for the possibility to use other URN schemes. "If a URN scheme other than UUID is used, the UA MUST only use URNs for which an RFC (from the IETF stream) defines how the specific URN needs to be constructed and used in the "+sip.instance" Contact header field parameter for outbound behavior." This specification meets this requirement by specifying how the GSMA IMEI URN is used in the "+sip.instance" Contact header field parameter for outbound behavior, and draft-montemurro-gsma-imei-urn-18 [2] specifies how the GSMA IMEI URN is constructed. The GSMA IMEI is a URN for the IMEI a globally unique identifier that identifies mobile devices used in the Global System for Mobile communications(GSM), Universal Mobile Telecommunications System (UMTS) and 3GPP LTE (Long Term Evolution)networks. The IMEI allocation is managed by the GSMA to ensure that the IMEI values are globally unique. Details of the formatting of the IMEI as a URN are specified in draft-montemurro-gsma-imei-urn-18 [2] and the definition of the IMEI is contained in 3GPP TS 23.003 [10]. Further details about the GSMA role in allocating the IMEI and the IMEI allocation guidelines can be found in GSMA PRD TS.06 [11]. 2. 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 RFC 2119 [7]. Allen Expires May 24, 2014 [Page 3] Internet-Draft Using IMEI URN as an Instance ID November 2013 3. Background GSM, UMTS and LTE capable mobile devices represent 90% of the mobile devices in use worldwide. Every manufactured GSM, UMTS or LTE mobile device has an allocated IMEI that uniquely identifies this specific mobile device. Amongst other things in some regulatory jurisdictions the IMEI is used to identify that a stolen mobile device is being used, to help to identify the subscription that is using it and to prevent use of the mobile device. Whilst GSM was originally a circuit switched system, enhancements such as GPRS (General Packet Radio Service) and UMTS have added IP data capabilities which along with the definition of the IP (Internet Protocol) Multimedia Subsystem (IMS) have made SIP based calls and IP multimedia sessions from mobile devices possible. The latest enhancement known as LTE introduces even higher data rates and dispenses with the circuit switched infrastructure completely. This means that with LTE networks, voice calls will need to be conducted using IP and IMS. However, the transition to all IP, SIP based IMS networks worldwide will take a great many years and mobile devices being mobile will need to operate in both IP/SIP/IMS mode and circuit switched mode. This means that calls and sessions will need to be handed over between IP/SIP/IMS mode and circuit switched mode mid-call or mid-session. Also since many existing GSM and UMTS radio access networks are unable to support IP/SIP/IMS based voice services in a commercially acceptable manner, some sessions could have some media types delivered via IP/IMS simultaneously with voice media delivered via the circuit switched domain to the same mobile device. To achieve this the mobile device is needs to be simultaneously attached via both the IP/SIP/IMS domain and the circuit switched domain. To meet this need 3GPP has specified how to maintain session continuity between the IP/SIP/IMS domain and the circuit switched domain in 3GPP TS 24.237 [12] and how to access IMS hosted services via both the IP/SIP/IMS domain and the circuit switched domain in 3GPP TS 24.292 [13]. In order for the mobile device to access SIP/IMS services via the circuit switched domain 3GPP has specified a MSC (Mobile Switching Center) server enhanced for ICS (IMS centralized services) and a MSC server enhanced for SR-VCC (Single Radio Voice Call Continuity) that control mobile voice call setup over the circuit switched radio access while establishing the corresponding voice session in the core network using SIP/IMS. To enable this, the MSC server enhanced for ICS or MSC server enhanced for SR-VCC, perform SIP registration on behalf of the mobile device which is also simultaneously directly registered with the IP/SIP/IMS domain. The only mobile device Allen Expires May 24, 2014 [Page 4] Internet-Draft Using IMEI URN as an Instance ID November 2013 identifier that is transportable using GSM/UMTS/LTE signaling is the IMEI therefore the instance-id included by the MSC server enhanced for ICS or the MSC server enhanced for SR-VCC when acting on behalf of the mobile device, and the instance-id directly included by the mobile device both need to be based on the IMEI. Additionally in order to meet the above requirements, the same IMEI that is obtained from the circuit switched signaling by the MSC server needs to be obtainable from SIP signaling so that that it can be determined that both the SIP signaling and circuit switched signaling originate from the same mobile device. 3GPP TS 24.237 [12] and 3GPP TS 24.292 [13] already specify the use of the URN namespace for the GSMA IMEI URN as specified in draft-montemurro-gsma-imei-urn-18 [2] as the instance-id used by GSM/ UMTS/LTE mobile devices, the MSC server enhanced for SR-VCC and the MSC server enhanced for ICS, for SIP/IMS registrations and emergency related SIP requests for these reasons. 4. 3GPP Use Cases 1. The mobile device includes its IMEI in the SIP REGISTER request so that the SIP registrar can perform a check of the Equipment Identity Register (EIR) to verify if this mobile device is allowed or barred from accessing the network for non-emergency services (e.g., because it has been stolen). If the mobile device is not allowed to access the network for non-emergency services the SIP registrar can reject the registration. Thus a barred mobile device is prevented from accesssing the network for non-emergency services. 2. The mobile device includes its IMEI in SIP INVITE requests used to establish emergency sessions. This is so that the PSAP (Public Safety Answering Point) can obtain the IMEI of the mobile device for identification purposes if required by regulations. 3. The inclusion by the mobile device of its IMEI in SIP INVITE requests used to establish emergency sessions is also used in the cases of unauthenticated emergency sessions to enable the network to identify the mobile device. This is especially important if the unauthenticated emergency session is handed over from the packet switched domain to the circuit switched domain. In this scenario the IMEI is the only identifier that is common to both domains that the Emergency Access Transfer Function (EATF) in the network, that coordinates the transfer between domains, can use to identify that Allen Expires May 24, 2014 [Page 5] Internet-Draft Using IMEI URN as an Instance ID November 2013 the circuit switched call is from the same mobile device that was in the emergency session in the packet switched domain. 5. User Agent Client Procedures A UAC that has an IMEI as specified in 3GPP TS 23.003 [10] that is registering with a 3GPP IMS network MUST include in the "sip.instance" media feature tag the GSMA IMEI URN according to the syntax specified in draft-montemurro-gsma-imei-urn-18 [2] when performing the registration procedures specified in RFC 5626 [1] or RFC 5627 [3] or any other procedure requiring the inclusion of the "sip.instance" media feature tag. The UAC SHOULD NOT include the optional "svn" parameter in the GSMA IMEI URN in the "sip.instance" media feature tag, since the software version can change as a result of upgrades to the device firmware which would create a new instance-id. Any future non zero values of the "vers" parameter, or the future definition of additional parameters for the GSMA IMEI URN that are intended to be used as part of an instance-id will require an update to be made to this RFC. The UAC MUST provide character-by- character identical URNs in each registration according to RFC 5626 [1]. Hence, any optional or variable components of the URN (e.g., the "vers" parameter) MUST be presented with the same values and in the same order in every registration as in the first registration. A UAC MUST only use the GSMA IMEI URN as an instance-id when registering with a 3GPP IMS network. When registering with a non- 3GPP IMS network a UAC SHOULD use a UUID as an instance-id as specified in RFC 5626 [1]. A UAC MUST NOT include the "sip.instance" media feature tag containing the GSMA IMEI URN in the Contact header field of non- REGISTER requests except when the request is related to an emergency session. Regulatory requirements can require the IMEI to be provided to the Public Safety Answering Point (PSAP). Any future exceptions to this prohibition require a RFC that addresses how privacy is not violated by such a usage. 6. User Agent Server Procedures A UAS MUST NOT include its "sip.instance" media feature tag containing the GSMA IMEI URN in the Contact header field of responses except when the response is related to an emergency session. Regulatory requirements can require the IMEI to be provided to the Public Safety Answering Point(PSAP). Any future exceptions to this prohibition require a RFC that addresses how privacy is not violated Allen Expires May 24, 2014 [Page 6] Internet-Draft Using IMEI URN as an Instance ID November 2013 by such a usage. 7. 3GPP SIP Registrar Procedures In 3GPP IMS when the SIP Registrar receives in the Contact header field a "sip.instance" media feature tag containing the GSMA IMEI URN according to the syntax specified in draft-montemurro-gsma-imei-urn-18 [2] the SIP registrar follows the procedures specified in RFC 5626 [1]. If the UA indicates that it supports the extension in RFC 5627 [3] and the SIP Registrar allocates a public GRUU according to the procedures specified in RFC 5627 [3] the instance-id MUST be obfuscated when creating the "gr" parameter in order not to reveal the IMEI to other UAs when the public GRUU is included in non-REGISTER requests and responses. 3GPP TS 24.229 [8] subclause 5.4.7A.2 specifies the mechanism for obfuscating the IMEI when creating the "gr" parameter. 8. IANA considerations This document defines no items requiring action by IANA. 9. Security considerations Because IMEIs like other formats of instance-ids can be loosely correlated to a user, they need to be treated as any other personally identifiable information. In particular, the "sip.instance" media feature tag containing the GSMA IMEI URN MUST NOT be included in requests or responses intended to convey any level of anonymity, as this could violate the users privacy. RFC 5626 [1] states "One case where a UA could prefer to omit the "sip.instance" media feature tag is when it is making an anonymous request or some other privacy concern requires that the UA not reveal its identity". The same concerns apply when using the GSMA IMEI URN as an instance-id. Publication of the GSMA IMEI URN to networks that the UA is not attached to or the UA does not have a service relationship with is a security breach and the "sip.instance" media feature tag MUST NOT be forwarded by the service provider's network elements when forwarding requests or responses towards the destination UA. Additionally, an instance-id containing the GSMA IMEI URN identifies a mobile device and not a user. The instance-id containing the GSMA IMEI URN MUST NOT be used alone as an address for a user or as an identification credential for a user. The GRUU mechanism specified in RFC 5627 [3] provides a means to create URIs that address the user at a specific device or User Agent. Allen Expires May 24, 2014 [Page 7] Internet-Draft Using IMEI URN as an Instance ID November 2013 In order to protect the "sip.instance" media feature tag containing the GSMA IMEI URN from being tampered with, those REGISTER requests containing the GSMA IMEI URN MUST be sent using a security mechanism such as TLS (RFC 4346 [5]) or another security mechanism that provides equivalent levels of protection. 10. Acknowledgements The author would like to thank Paul Kyzivat, Dale Worley, Cullen Jennings, Adam Roach, Keith Drage, Mary Barnes, Peter Leis, James Yu, S. Moonesamy, Roni Even, and Tim Bray for reviewing this draft and providing their comments. 11. References 11.1. Normative references [1] Jennings, C., Mahy, R., and F. Audet, "Managing Client- Initiated Connections in the Session Initiation Protocol (SIP)", RFC 5626, October 2009. [2] Montemurro, M., "A Uniform Resource Name Namespace For The Global System for Mobile communications Association (GSMA) and the International Mobile station Equipment Identity(IMEI), work in progress", Internet Draft draft-montemurro-gsma-imei-urn-18, November 2013. [3] Rosenberg, J., "Obtaining and Using Globally Routable User Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)", RFC 5627, October 2009. [4] Moats, R., "URN Syntax", RFC 2141, May 1997. [5] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. [6] Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, July 2005. [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [8] 3GPP, "TS 24.229: IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3 (Release 8)", 3GPP 24.229, September 2013, Allen Expires May 24, 2014 [Page 8] Internet-Draft Using IMEI URN as an Instance ID November 2013 . [9] 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. 11.2. Informative references [10] 3GPP, "TS 23.003: Numbering, addressing and identification (Release 8)", 3GPP 23.003, September 2013, . [11] GSMA Association, "IMEI Allocation and Approval Guidelines", PRD TS.06 (DG06) version 6.0, July 2011, . [12] 3GPP, "TS 24.237: Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 (Release 8)", 3GPP 24.237, September 2013, . [13] 3GPP, "TS 24.292: IP Multimedia (IM) Core Network (CN) subsystem Centralized Services (ICS); Stage 3 (Release 8)", 3GPP 24.292, June 2013, . Author's Address Andrew Allen (editor) Blackberry 1200 Sawgrass Corporate Parkway Sunrise, Florida 33323 USA Email: aallen@blackberry.com Allen Expires May 24, 2014 [Page 9]