Dispatch Working Group A. Allen, Ed. Internet-Draft Research in Motion (RIM) Intended status: Informational February 8, 2013 Expires: August 12, 2013 Using the International Mobile station Equipment Identity(IMEI)URN as an Instance ID draft-allen-dispatch-imei-urn-as-instanceid-07 Abstract This specification defines how the Uniform Resource Name namespace 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 as specified in RFC 5626 [1] and also as used by RFC 5627 [2]. Its purpose is to fulfil the requirements in RFC 5626 [1] that state "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." 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 August 12, 2013. 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 August 12, 2013 [Page 1] Internet-Draft Using IMEI URN as an Instance ID February 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 . . . . . . . . . . . . . . . . . 5 6. User Agent Server Procedures . . . . . . . . . . . . . . . . . 6 7. 3GPP Registrar Procedures . . . . . . . . . . . . . . . . . . . 7 8. Security considerations . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative references . . . . . . . . . . . . . . . . . . . 8 10.2. Informative references . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Allen Expires August 12, 2013 [Page 2] Internet-Draft Using IMEI URN as an Instance ID February 2013 1. Introduction This specification defines how the Uniform Resource Name namespace reserved for GSMA identities and its sub namespace for the IMEI (International Mobile station Equipment Identity) as defined in draft-montemurro-gsma-imei-urn-11 [3] can be used as an instance-id as specified in RFC 5626 [1] and also as used by RFC 5627 [2]. RFC 5626 [1] defines the "+sip.instance" Contact header field parameter which contains a URN as per RFC 2141 [4] defined as an instance-id that uniquely identifies a specific UA instance. This instance-id is used as defined in RFC 5626 [1] so that registrar can recognize that the contacts from multiple registrations correspond to the same UA. The instance-ID is also used as defined by RFC 5627 [2] 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] defines that a UA SHOULD create a Universally Unique Identifier (UUID) URN as defined in RFC 4122 [7] as its instance-id but allows for the possibility of other URN schemes to be used. "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-11 [3] defines how the GSMA IMEI URN is constructed The GSMA IMEI is an identifier for a namespace for the IMEI a globally unique identifier that identifies Mobile Equipment used in 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 defined in draft-montemurro-gsma-imei-urn-11 [3] and the definition of the IMEI is contained in 3GPP TS 23.003 [8]. Further details about the GSMA role in allocating the IMEI and the IMEI allocation guidelines can be found in GSMA PRD DG.06 [9] 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 [5]. Allen Expires August 12, 2013 [Page 3] Internet-Draft Using IMEI URN as an Instance ID February 2013 3. Background GSM and UMTS capable mobile devices represent 90% of the mobile devices in use worldwide. GSM and UMTS mobile devices each have an IMEI allocated which uniquely identifies the mobile device from all other GSM/UMTS mobile devices deployed. Amongst other things in some regulatory jurisdictions the IMEI is used to identify that a stolen mobile is being used to help to identify the subscription that is using it and to prevent its use. 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 Multimedia Subsystem (IMS) has made SIP based calls and IP multimedia sessions from mobile devices possible. The latest enhancment known as LTE will introduce even higher data rates and dispenses with the circuit switched domain completely meaning that with LTE 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. In fact calls and sessions will need to be handed over between IP/SIP/IMS mode and circuit switched mode during a call. Also as 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 can have some media types delivered via IP/IMS simultaneously with voice media delivered via circuit switched with the same mobile device 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 [10] and how to access IMS hosted services via both the IP/ SIP/IMS domain and the circuit switched domain in 3GPP TS 24.292 [11]. In order for the the mobile device to access SIP/IMS services via the circuit switched domain 3GPP has defined a MSC (Mobile Switching Center) server enhanced for ICS (IMS centralized services)which controls 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 performs SIP registration on behalf of the mobile device which can also be simultaneously directly registered with the IP/SIP/IMS domain. The only mobile device identifier that is transportable using GSM/UMTS/LTE signaling is the IMEI therefore both the instance-id included by the MSC server enhanced for ICS when acting on behalf of the mobile device and the instance-id included by the mobile device directly needs to be based on the IMEI. Additionally in order to meet the above regulatory requirements, the Allen Expires August 12, 2013 [Page 4] Internet-Draft Using IMEI URN as an Instance ID February 2013 IMEI that is obtained from the circuit switched signaling needs to be obtainable from SIP signaling. 3GPP TS 24.237 [10] and 3GPP TS 24.292 [11] already define the use of the URN namespace for the GSMA and IMEI as defined in draft-montemurro-gsma-imei-urn-11 [3] as the instance-id used by mobile devices and the MSC server enhanced for ICS for SIP/IMS registrations for these reasons. 4. 3GPP Use Cases 1. The mobile device includes its IMEI in the SIP REGISTER request so that the registrar can perform a check of the Equipment Identity Registry (EIR) to verify if the mobile device is allowed or barred from using the network (e.g because it has been stolen). If the mobile device is not allowed to use the network the registrar can reject the registration. Thus a barred device is prevented from using the network. 2. The mobile device includes its IMEI in SIP INVITE requests used to establish emergency sessions. This 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 circuit switched domain as in this scenario the IMEI is the only common means for identifying 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 defined in 3GPP TS 23.003 [8] 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 defined in draft-montemurro-gsma-imei-urn-11 [3] when performing the registration procedures defined in RFC 5626 [1] or RFC 5627 [2] or any other procedure requiring including the Allen Expires August 12, 2013 [Page 5] Internet-Draft Using IMEI URN as an Instance ID February 2013 "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. The UAC MUST provide lexically equivalent URNs in each registration [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 defined in RFC 5626 [1]. A UAC MUST NOT include its "sip.instance" media feature tag containing the GSMA IMEI URN in the Contact header field of non- register requests unless the UAC is certain that the request will be sent via a trusted intermediary that will remove the "sip.instance" media feature tag prior to forwarding the request towards the destination. In order to ensure that all requests containing the "sip.instance" media feature tag are forwarded via the trusted intermediary the UAC MUST first have verified that the trusted intermediary is present (e.g. first contacted via a registration or configuration procedure). The exception to this is when the request is related to an emergency session when regulatory requirements can require the IMEI to be provided to the Public Safety Answering Point (PSAP). 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 unless the UAS is certain that the response will be sent via a trusted intermediary that will remove the "sip.instance" media feature tag prior to forwarding the response towards the destination. In order to ensure that all responses containing the "sip.instance" media feature tag are forwarded via the trusted intermediary the UAS MUST first have verified that the trusted intermediary is present (e.g. first contacted via a registration or configuration procedure). The exception to this is when the response is related to an emergency session when regulatory requirements can require the IMEI to be provided to the Public Safety Answering Point(PSAP). Allen Expires August 12, 2013 [Page 6] Internet-Draft Using IMEI URN as an Instance ID February 2013 7. 3GPP Registrar Procedures In 3GPP IMS when the Registrar receives in the Contact header field a "sip.instance" media feature tag containing the GSMA IMEI URN according to the syntax defined in draft-montemurro-gsma-imei-urn-11 [3] the registrar follows the procedures defined in RFC 5626 [1] and RFC 5627 [2] if those extensions are supported and indicated as supported by the UA. If the Registrar allocates a public GRUU according to the procedures defined in RFC 5627 [2] 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. 3GPP TS 24.229 [6] subclause 5.4.7A.2 defines the mechanism for obfuscating the IMEI when creating the "gr" parameter. 8. 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. 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. In order to protect from tampering the REGISTER requests containing the GSMA IMEI URN MUST be sent using a security mechanism such as TLS [12] (or another security mechanism that provides equivalent levels of protection). 9. Acknowledgements The author would like to thank Paul Kyzivat, Dale Worley, Cullen Jennings, Adam Roach, and Keith Drage for reviewing this draft and providing their comments. 10. References Allen Expires August 12, 2013 [Page 7] Internet-Draft Using IMEI URN as an Instance ID February 2013 10.1. 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] Rosenberg, J., "Obtaining and Using Globally Routable User Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)", RFC 5627, October 2009. [3] Montemurro, M., "A Uniform Resource Name Namespace For The GSM Association (GSMA) and the International Mobile station Equipment Identity(IMEI), work in progress", Internet Draft draft-montemurro-gsma-imei-urn-12, February 2013. [4] Moats, R., "URN Syntax", RFC 2141, May 1997. [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [6] 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, December 2012, . 10.2. Informative references [7] Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, July 2005. [8] 3GPP, "TS 23.003: Numbering, addressing and identification (Release 8)", 3GPP 23.003, December 2012, . [9] GSMA Association, "IMEI Allocation and Approval Guidelines", PRD TS.06 (DG06) version 6.0, July 2011, . [10] 3GPP, "TS 24.237: Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 (Release 8)", 3GPP 24.237, December 2012, . [11] 3GPP, "TS 24.292: IP Multimedia (IM) Core Network (CN) subsystem Centralized Services (ICS); Stage 3 (Release 8)", 3GPP 24.292, December 2012, Allen Expires August 12, 2013 [Page 8] Internet-Draft Using IMEI URN as an Instance ID February 2013 . [12] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. Author's Address Andrew Allen (editor) Research in Motion (RIM) 1200 Sawgrass Corporate Parkway Sunrise, Florida 33323 USA Phone: unlisted Fax: unlisted Email: aallen@rim.com Allen Expires August 12, 2013 [Page 9]