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Versions: 00 01 02 03 04 05 06 08 09 10 11 12 13 RFC 7255

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


Using the International Mobile station Equipment Identity(IMEI)URN as an
                              Instance ID
             draft-allen-dispatch-imei-urn-as-instanceid-09

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
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   This Internet-Draft will expire on November 7, 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



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

   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7

   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     10.1.  Normative references . . . . . . . . . . . . . . . . . . . 7
     10.2.  Informative references . . . . . . . . . . . . . . . . . . 8

   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8


















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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-14 [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-14 [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-14 [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].



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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



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   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-14 [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-14 [3] when
   performing the registration procedures defined in RFC 5626 [1] or RFC
   5627 [2] or any other procedure requiring including the



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   "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 its "sip.instance" media feature tag
   containing the GSMA IMEI URN in the Contact header field of non-
   register requests or responses except when the request or response is
   related to an emergency session when 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 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 when
   regulatory requirements can require the IMEI to be provided to the
   Public Safety Answering Point(PSAP).


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-14
   [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



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   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

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



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         Equipment Identity(IMEI), work in progress", Internet
         Draft draft-montemurro-gsma-imei-urn-14, May 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,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.229/>.

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,
         <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,
         December 2012,
         <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, December 2012,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.292/>.

   [12]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
         RFC 2246, January 1999.











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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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