Using the International Mobile station Equipment Identity(IMEI)URN as an Instance ID
draft-allen-dispatch-imei-urn-as-instanceid-10

Dispatch Working Group                                     A. Allen, Ed.
Internet-Draft                                                Blackberry
Intended status: Informational                              July 6, 2013
Expires: January 7, 2014

Using the International Mobile station Equipment Identity(IMEI)URN as an
                              Instance ID
             draft-allen-dispatch-imei-urn-as-instanceid-10

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

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   publication of this document.  Please review these documents
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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 . . . . . . . . . . . . . . . . . . . 6

   8.  IANA considerations . . . . . . . . . . . . . . . . . . . . . . 7

   9.  Security considerations . . . . . . . . . . . . . . . . . . . . 7

   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7

   11. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     11.1.  Normative references . . . . . . . . . . . . . . . . . . . 8
     11.2.  Informative references . . . . . . . . . . . . . . . . . . 8

   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9

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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-15 [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-15 [3] defines how the
   GSMA IMEI URN is constructed.

   The GSMA IMEI URN is a namespace 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
   defined in draft-montemurro-gsma-imei-urn-15 [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 TS.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].

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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 which uniquely identifies this specific
   mobile device.  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) have made SIP based calls and IP
   multimedia sessions from mobile devices possible.  The latest
   enhancement known as LTE will introduce even higher data rates and
   dispenses with the circuit switched infrastructure 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 the circuit switched
   domain 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 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) and a MSC
   server enhanced for SR-VCC (Single Radio Voice Call Continuity) which
   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 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 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 included by the mobile
   device directly both need to be based on the IMEI.

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   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 [10] and 3GPP TS 24.292 [11] already define the use of
   the URN namespace for the GSMA IMEI URN as defined in
   draft-montemurro-gsma-imei-urn-15 [3] 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 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 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 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

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   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-15 [3] when
   performing the registration procedures defined in RFC 5626 [1] or RFC
   5627 [2] 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 value of the "vers" parameter other than
   equal to 0 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
   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 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
   by such a usage.

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-15

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   [3] the registrar follows the procedures defined in RFC 5626 [1].  If
   the UA indicates that it supports the extension in RFC 5627 [2] and
   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 and
   responses. 3GPP TS 24.229 [6] subclause 5.4.7A.2 defines 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.  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 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 [12] (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 and James
   Yu for reviewing this draft and providing their comments.

11.  References

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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]   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-15, July 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, June 2013,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.229/>.

11.2.  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,
         <ftp://ftp.3gpp.org/Specs/archive/23_series/23.003/>.

   [9]   GSMA Association, "IMEI Allocation and Approval Guidelines",
         PRD TS.06 (DG06) version 6.0, July 2011, <http://www.gsma.com/
         newsroom/wp-content/uploads/2012/06/
         ts0660tacallocationprocessapproved.pdf>.

   [10]  3GPP, "TS 24.237: Mobile radio interface Layer 3 specification;
         Core network protocols; Stage 3 (Release 8)", 3GPP 24.237,
         June 2013,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.237/>.

   [11]  3GPP, "TS 24.292: IP Multimedia (IM) Core Network (CN)
         subsystem Centralized Services (ICS); Stage 3 (Release 8)",
         3GPP 24.292, June 2013,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.292/>.

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   [12]  Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
         Protocol Version 1.1", RFC 4346, April 2006.

Author's Address

   Andrew Allen (editor)
   Blackberry
   1200 Sawgrass Corporate Parkway
   Sunrise, Florida  33323
   USA

   Phone: unlisted
   Fax:   unlisted
   Email: aallen@blackberry.com

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