Using the International Mobile station Equipment Identity (IMEI) Uniform Resource Name (URN) as an Instance ID
draft-allen-dispatch-imei-urn-as-instanceid-11

Dispatch Working Group                                     A. Allen, Ed.
Internet-Draft                                                Blackberry
Intended status: Informational                          October 18, 2013
Expires: April 21, 2014

    Using the International Mobile station Equipment Identity (IMEI)
             Uniform Resource Name (URN) as an Instance ID
             draft-allen-dispatch-imei-urn-as-instanceid-11

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

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   (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  . . . . . . . . . . . . . . . . . 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

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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-17 [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-17 [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-17 [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].

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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 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

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   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-17 [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 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.

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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-17 [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
   by such a usage.

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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-17 [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.

   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

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   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 GSM
         Association (GSMA) and the International Mobile  station
         Equipment Identity(IMEI), work in progress", Internet
         Draft draft-montemurro-gsma-imei-urn-17, October 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,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.229/>.

   [9]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:

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

   [11]  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>.

   [12]  3GPP, "TS 24.237: Mobile radio interface Layer 3 specification;
         Core network protocols; Stage 3 (Release 8)", 3GPP 24.237,
         September 2013,
         <ftp://ftp.3gpp.org/Specs/archive/24_series/24.237/>.

   [13]  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/>.

Author's Address

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

   Email: aallen@blackberry.com

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