GSMA IMEI URN: A Uniform Resource Name Namespace for the Global System for Mobile Communications Association (GSMA) and the International Mobile station Equipment Identity (IMEI)

Internet Engineering Task Force (IETF)                M. Montemurro, Ed.
Request for Comments: 7254                                      A. Allen
Category: Informational                                       Blackberry
ISSN: 2070-1721                                              D. McDonald
                                                                  Eircom
                                                               P. Gosden
                                                         GSM Association
                                                                May 2014


                   A Uniform Resource Name Namespace
   for the Global System for Mobile Communications Association (GSMA)
     and the International Mobile station Equipment Identity (IMEI)

Abstract

   This specification defines a Uniform Resource Name (URN) namespace
   for the Global System for Mobile Communications Association (GSMA)
   and a Namespace Specific String (NSS) for the International Mobile
   station Equipment Identity (IMEI), as well as an associated parameter
   for the International Mobile station Equipment Identity and Software
   Version number (IMEISV).  The IMEI and IMEISV were introduced as part
   of the specification for the GSM and are also now incorporated by the
   3rd Generation Partnership Project (3GPP) as part of the 3GPP
   specification for GSM, Universal Mobile Telecommunications System
   (UMTS), and 3GPP Long Term Evolution (LTE) networks.  The IMEI and
   IMEISV are used to uniquely identify Mobile Equipment within these
   systems and are managed by the GSMA.  URNs from this namespace almost
   always contain personally identifiable information and need to be
   treated accordingly.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7254.

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Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Namespace Registration Template .................................4
   4. Specification ...................................................8
      4.1. IMEI Parameters ............................................8
      4.2. IMEI Format ................................................9
           4.2.1. Type Allocation Code (TAC) ..........................9
           4.2.2. Serial Number (SNR) .................................9
           4.2.3. Spare ..............................................10
           4.2.4. Binary Encoding ....................................10
      4.3. IMEISV Format .............................................10
           4.3.1. Type Allocation Code (TAC) .........................10
           4.3.2. Serial Number (SNR) ................................11
           4.3.3. Software Version Number (SVN) ......................11
           4.3.4. Binary Encoding ....................................11
   5. Community Considerations .......................................11
   6. Namespace Considerations .......................................12
   7. IANA Considerations ............................................12
   8. Security and Privacy Considerations ............................12
   9. Acknowledgements ...............................................14
   10. References ....................................................14
      10.1. Normative References .....................................14
      10.2. Informative References ...................................15

1.  Introduction

   This specification defines a Uniform Resource Name (URN) namespace
   for the Global System for Mobile Communications Association (GSMA)
   and a Namespace Specific String (NSS) for the International Mobile
   station Equipment Identity (IMEI), as well as an associated parameter
   for the International Mobile station Equipment Identity and Software
   Version number (IMEISV) as per the namespace registration requirement
   found in RFC 3406 [1].  The Namespace Identifier (NID) 'gsma' is for
   identities used in GSM, Universal Mobile Telecommunications System
   (UMTS), and Long Term Evolution (LTE) networks.  The IMEI and the
   IMEISV are managed by the GSMA, so this NID is managed by the GSMA.
   While this specification currently defines only the 'imei' NSS under
   the 'gsma' NID, additional NSS under the 'gsma' NID may be specified
   in the future by the GSMA, using the procedure for URN NSS changes
   and additions (currently through the publication of future
   Informational RFCs approved by IETF consensus).

   The IMEI is 15 decimal digits long and includes a Type Allocation
   Code (TAC) of 8 decimal digits and a Serial Number (SNR) of 6 decimal
   digits plus a Spare decimal digit.  The TAC identifies the type of
   the Mobile Equipment and is chosen from a range of values allocated
   to the Mobile Equipment manufacturer in order to uniquely identify
   the model of the Mobile Equipment.  The SNR is an individual serial
   number that uniquely identifies each Mobile Equipment device within
   the TAC.  The Spare digit is used as a Check digit to validate the
   IMEI and is always set to the value 0 when transmitted by the Mobile
   Equipment.

   The IMEISV is 16 decimal digits long and includes the TAC and SNR,
   same as for the IMEI, but also includes a 2 decimal digit Software
   Version Number (SVN), which is allocated by the Mobile Equipment
   manufacturer to identify the software version of the Mobile
   Equipment.

   The information here is meant to be a concise guide for those wishing
   to use the IMEI and IMEISV as URNs.  Nothing in this document should
   be construed to override 3GPP Technical Specification (TS) 23.003
   [2], which specifies the IMEI and IMEISV.

   The GSMA is a global trade association representing nearly 800 mobile
   phone operators across 220 territories and countries of the world.
   The primary goals of the GSMA are to ensure that mobile phones and
   wireless services work globally and are easily accessible.  Further
   details about the GSMA's role in allocating the IMEI and the IMEISV,
   as well as the IMEI and IMEISV allocation guidelines, can be found in
   GSMA Permanent Reference Document (PRD) TS.06 [3].

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 [4].

3.  Namespace Registration Template

   Namespace ID:  'gsma'

   Registration Information:

   Registration version number:  1

   Registration date:  2014-01-12
   Declared registrant of the namespace:

   Registering organization:

   Name:  GSM Association

   Address:  1st Floor, Mid City Place,

      71 High Holborn, London, England

   Designated contact person:

   Name:  Paul Gosden

   Coordinates:  pgosden@gsma.com

   Declaration of syntactic structure:

      The identifier is expressed in American Standard Code for
      Information Interchange (ASCII) characters and has a hierarchical
      structure expressed using the Augmented Backus-Naur Form (ABNF)
      defined in RFC 5234 [5], as follows:

         gsma-urn              = "urn:" gsma-NID ":" gsma-NSS
         gsma-NID              = "gsma"
         gsma-NSS              = imei-specifier / future-gsma-specifier
         imei-specifier        = "imei:" ( imeival / ext-imei )
                                              [ ";" sw-version-param ]
                                              [ ";" imei-version-param ]
         ext-imei = gsma-defined-nonempty ;GSMA defined and
                                          ;IETF consensus
                                          ;required
         sw-version-param      = "svn=" software-version
         imei-version-param    = "vers=" imei-version-val
         software-version      = 2DIGIT
         imei-version-val      = DIGIT
         future-gsma-specifier = future-specifier
                                           *( ";" future-param )
         future-specifier      = gsma-defined-nonempty ;GSMA defined

         future-param          = par-name [ EQUAL par-value ]
         par-name              = gsma-defined-nonempty
         par-value             = gsma-defined-nonempty
         EQUAL                 = "="
         gsma-defined-nonempty = 1*gsma-urn-char
         gsma-urn-char         = ALPHA / DIGIT
                                 / "-" / "." / "_" / "%" / ":"

      An NSS for the IMEI is defined under the 'gsma' NID.

      An IMEI is an identifier under the 'gsma' NID that uniquely
      identifies the mobile devices used in the GSM, UMTS, and LTE
      networks.

      The representation of the IMEI is defined in 3GPP TS 23.003 [2].
      To accurately represent an IMEI received in a cellular signaling
      message (see 3GPP TS 24.008 [6]) as a URN, it is necessary to
      convert the received binary (Binary Coded Decimal (BCD)) encoded
      bit sequence to a decimal digit string representation.  Each field
      has its representation for humans as a decimal digit string with
      the most significant digit first.

      The following ABNF includes the set of core rules in RFC 5234 [5];
      the core rules are not repeated here.

      A URN with the 'imei' NSS contains one 'imeival', and its formal
      definition is provided by the following ABNF (RFC 5234) [5]:

      imeival  =  tac "-" snr "-" spare

      tac      = 8DIGIT

      snr      = 6DIGIT

      spare    = DIGIT

      <future-gsma-specifier> and <gsma-defined-nonempty> can comprise
      any ASCII characters compliant with the above ABNF.

      The GSMA will take responsibility for the 'gsma' namespace,
      including the 'imei' NSS.

      Additional NSS may be added for future identifiers needed by the
      GSMA, at their discretion.  Only URNs with the 'imei' NSS are
      considered to be "GSMA IMEI URNs", and use in IETF protocols of
      other NSS that might be defined in the future will require IETF
      consensus.

   Relevant ancillary documentation:

      See IMEI Allocation and Approval Guidelines (GSMA PRD TS.06) [3]
      and 3GPP TS 23.003 [2].

   Identifier uniqueness considerations:

      Identifiers under the 'gsma' NID are defined and assigned by the
      GSMA after ensuring that the URNs to be assigned are unique.
      Uniqueness is achieved by checking against the IANA registry of
      previously assigned names.

      Procedures are in place to ensure that each IMEI is uniquely
      assigned by the Mobile Equipment manufacturer so that it is
      guaranteed to uniquely identify that particular Mobile Equipment
      device.

      Procedures are in place to ensure that each IMEISV is uniquely
      assigned by the Mobile Equipment manufacturer so that it is
      guaranteed to uniquely identify that particular Mobile Equipment
      device and the specific software version installed.

   Identifier persistence considerations:

      The GSMA is committed to maintaining uniqueness and persistence of
      all resources identified by assigned URNs.

      As the NID sought is 'gsma' and "GSMA" is the long-standing
      acronym for the trade association that represents the mobile phone
      operators, the URN should also persist indefinitely (at least as
      long as there is a need for its use).  The assignment process
      guarantees that names are not reassigned.  The binding between the
      name and its resource is permanent.

      The TAC and SNR portions of the IMEI and IMEISV are permanently
      stored in the Mobile Equipment, so they remain persistent as long
      as the Mobile Equipment exists.  The process for TAC and SNR
      assignment is documented in GSMA PRD TS.06 [3], and once assigned,
      the TAC and SNR values are not reassigned to other Mobile
      Equipment devices.  The SVN portion of the IMEISV may be modified
      by software when new versions are installed but should be
      persistent for the duration of the installation of that specific
      version of software.

   Process of identifier assignment:

      The GSMA will manage the <NSS> (including 'imei') and
      <future-gsma-specifier> identifier resources to maintain
      uniqueness.

      The process for IMEI and IMEISV assignment is documented in GSMA
      PRD TS.06 [3].

   Process for identifier resolution:

      Since the 'gsma' NSS is not currently globally resolvable, this is
      not applicable.

   Rules for Lexical Equivalence:

      Two GSMA IMEI URNs are equivalent if they have the same 'imeival'
      value, and the same parameter values in the same sequential order,
      with the exception that the 'vers=0' parameter is to be ignored
      for the purposes of comparison.  All of these comparisons are to
      be case insensitive.

      Any identifier in the 'gsma' NSS can be compared using the normal
      mechanisms for percent-encoded UTF-8 strings (see RFC 3629 [7]).

   Conformance with URN Syntax:

      The string representation of the 'gsma' NID and of the 'imei' NSS
      is fully compatible with the URN syntax (see RFC 2141 [8]).

   Validation mechanism:

      The IMEI can be validated using the mechanism defined in Annex B
      of 3GPP TS 23.003 [2].  There is no mechanism defined to validate
      the SVN field of the IMEISV.

   Scope:  The GSMA URN is global in scope.

4.  Specification

4.1.  IMEI Parameters

   The optional 'vers' parameter and the 'ext-imei' field in the ABNF
   are included for extensibility of the 'imei' NSS -- for example, if
   the IMEI format is extended in the future (such as with additional
   digits or using hex digits).  In this case, the 'vers' parameter
   would contain a non-zero value and the 'ext-imei' would be further
   defined to represent the syntax of the extended IMEI format.  A value
   of the 'vers' parameter equal to 0 or the absence of the 'vers'
   parameter means the URN format is compliant with the format specified
   here.

   Any change to the format of the 'imei' NSS requires the use of the
   procedure for URN NSS changes and additions (currently through the
   publication of future Informational RFCs approved by IETF consensus).
   The use of the 'vers' parameter was chosen for extensibility instead
   of defining a new NSS (e.g., 'imei2') because it is likely that many
   applications will only need to perform string compares of the
   'imeival'.  So, even if the format or length of the 'imeival' changes
   in the future, such applications should continue to work without
   having to be updated to understand a new NSS.

   RFC 7255 [10] specifies how the GSMA IMEI URN can be used as an
   instance ID as specified in RFC 5626 [11].  Any future value of the
   'vers' parameter other than 0, or the definition of additional
   parameters that are intended to be used as part of an instance ID,
   will require an update to RFC 7255 [10].

   For example:

      urn:gsma:imei:90420156-025763-0;vers=0

   The IMEISV is an identifier that uniquely identifies mobile devices
   and their associated software versions used in the GSM, UMTS, and LTE
   networks.  The representation of the IMEISV is defined in 3GPP TS
   23.003 [2].

   To represent the IMEISV, the URN parameter 'svn' is appended to the
   GSMA IMEI URN and set equal to the decimal string representation of
   the two software version number (svn) digits in the IMEISV, and the
   Spare digit in the IMEI 'imeival' is set to zero.

   For example:

      urn:gsma:imei:90420156-025763-0;svn=42

4.2.  IMEI Format

4.2.1.  Type Allocation Code (TAC)

   The TAC is an 8 decimal digit value.  The TAC identifies the type of
   the Mobile Equipment and is chosen from a range of values allocated
   to the Mobile Equipment manufacturer in order to uniquely identify
   the model of the Mobile Equipment.

4.2.2.  Serial Number (SNR)

   The SNR is a 6 decimal digit value.  The SNR is an individual serial
   number that uniquely identifies each Mobile Equipment device within
   the TAC.

4.2.3.  Spare

   The Spare is a single decimal digit.  When the IMEI is stored on the
   Mobile Equipment and network equipment, it contains a value that is
   used as a Check digit and is intended to avoid manual reporting
   errors (e.g., when customers register stolen mobiles at the
   operator's customer care desk) and also to help guard against the
   possibility of incorrect entries being provisioned in the network
   equipment.  The Spare is always set to zero when transmitted by the
   Mobile Equipment (including when in the IMEI URN format).  Annex B of
   3GPP TS 23.003 [2] specifies a mechanism for computing the actual
   Check digit in order to validate the TAC and SNR.

4.2.4.  Binary Encoding

   When included in a cellular signaling message, the IMEI format is 15
   decimal digits encoded in 8 octets, using BCD as defined in 3GPP TS
   24.008 [6].  Figure 1 is an abstract representation of a BCD-encoded
   IMEI stored in memory (the actual storage format in memory is
   implementation specific).  In Figure 1, the most significant digit of
   the TAC is coded in the least significant bits of octet 1.  The most
   significant digit of the SNR is coded in the least significant bits
   of octet 5.  The Spare digit is coded in the least significant bits
   of octet 8.  When included in an identity element in a cellular
   signaling message, the most significant digit of the TAC is
   included in digit 1 of the identity element in Figure 10.5.4 of
   3GPP TS 24.008 [6].

       14 13 12 11 10  9  8  7  6  5  4  3  2  1  0  Decimal Digits
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
      |                       |                 | S|
      |            T          |          S      | p|
      |            A          |          N      | a|
      |            C          |          R      | r|
      |                       |                 | e|
      +--+-----+-----+-----+--+--+-----+-----+--+--+
         1     2     3     4     5     6     7     8  Octets

                           Figure 1: IMEI Format

4.3.  IMEISV Format

4.3.1.  Type Allocation Code (TAC)

   The TAC is the same as the TAC in the IMEI (see Section 4.2.1).

4.3.2.  Serial Number (SNR)

   The SNR is the same as the SNR in the IMEI (see Section 4.2.2).

4.3.3.  Software Version Number (SVN)

   The Software Version Number is allocated by the mobile device
   manufacturer to identify the software version of the mobile device.

4.3.4.  Binary Encoding

   When included in a cellular signaling message, the IMEISV format is
   16 decimal digits encoded in 8 octets using BCD as defined in 3GPP TS
   24.008 [6].  Figure 2 is an abstract representation of a BCD-encoded
   IMEISV stored in memory (the actual storage format in memory is
   implementation specific).  In Figure 2, the most significant digit of
   the TAC is coded in the most significant bits of octet 1.  The most
   significant digit of the SNR is coded in the most significant bits of
   octet 5.  The most significant digit of the SVN is coded in the most
   significant bits of octet 8.  When included in an identity element in
   a cellular signaling message, the most significant digit of the TAC
   is included in digit 1 of the identity element in Figure 10.5.4 of
   3GPP TS 24.008 [6].

       15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0  Decimal Digits
      +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
      |                       |                 |     |
      |            T          |          S      |  S  |
      |            A          |          N      |  V  |
      |            C          |          R      |  N  |
      |                       |                 |     |
      +-----+-----+-----+-----+-----+-----+-----+-----+
            1     2     3     4     5     6     7     8  Octets

                          Figure 2: IMEISV Format

5.  Community Considerations

   GSM, UMTS, and LTE mobile devices will be interoperating with
   Internet devices for a variety of voice and data services.  To do
   this, they need to make use of Internet protocols that will operate
   end to end between devices in GSM/UMTS/LTE networks and those in the
   general Internet.  Some of these protocols require the use of URNs as
   identifiers.  Within the GSM/UMTS/LTE networks, mobile devices are
   identified by their IMEI or IMEISV.  Internet users will need to be
   able to receive and include the GSMA URN in various Internet protocol
   elements to facilitate communication between pure Internet-based
   devices and GSM/UMTS/LTE mobile devices.  Thus, the existence and
   syntax of these namespaces need to be available to the general
   Internet community, and the namespace needs to be reserved with IANA
   in order to guarantee uniqueness and prevent potential namespace
   conflicts both within the Internet and within GSM/UMTS/LTE networks.
   Conversely, Internet implementations will not generally possess IMEI
   identifiers.  The identifiers generated by such implementations will
   typically be URNs within namespaces other than 'gsma' and may,
   depending on context, even be non-URN URIs.  Implementations are
   advised to be ready to process URIs other than 'gsma' namespaced
   URNs, so as to aid in interoperability.

6.  Namespace Considerations

   A URN was considered the most appropriate URI to represent the IMEI
   and IMEISV, as these identifiers may be used and transported
   similarly to the Universally Unique Identifier (UUID), which is
   defined as a URN in RFC 4122 [12].  Since specifications for
   protocols that are used to transport device identifiers often require
   the device identifier to be globally unique and in the URN format, it
   is necessary that the URN formats are defined to represent the IMEI
   and IMEISV.

7.  IANA Considerations

   In accordance with BCP 66 (RFC 3406) [1], IANA has registered the
   Formal URN Namespace 'gsma' in the "Uniform Resource Names (URN)
   Namespaces" registry, using the registration template presented in
   Section 3 of this document.

8.  Security and Privacy Considerations

   IMEIs (but with the Spare value set to the value of the Check digit)
   are displayable on most mobile devices and in many cases are printed
   on the case within the battery compartment.  Anyone with brief
   physical access to the mobile device can therefore easily obtain the
   IMEI.  Therefore, IMEIs MUST NOT be used as security capabilities
   (identifiers whose mere possession grants access).  Unfortunately,
   there are currently examples of some applications that are using the
   IMEI for authorization.  Also, some service provider's customer
   service departments have been known to use knowledge of the IMEI as
   "proof" that the caller is the legitimate owner of the mobile device.
   Both of these are inappropriate uses of the IMEI.

   While the specific software version of the mobile device only
   identifies the lower-layer software that has undergone and passed
   certification testing, and not the operating system or application
   software, the software version could identify software that is
   vulnerable to attacks or is known to contain security holes.

   Therefore, the IMEISV MUST only be delivered to trusted entities
   within carrier networks and not provided to the Internet at large, as
   it could help a malicious device identify that the mobile device is
   running software that is known to be vulnerable to certain attacks.
   This concern is similar to concerns regarding the use of the
   User-Agent header in the Session Initiation Protocol (SIP) as
   specified in RFC 3261 [13].  Therefore, the IMEISV (that is, the IMEI
   URN with a 'svn' parameter) MUST NOT be delivered to devices that are
   not trusted.  IMEIs are almost always personally identifiable
   information, and so these URNs MUST be treated as personally
   identifiable information in all cases.  In order to prevent violating
   a user's privacy, the IMEI URN MUST NOT be included in messages
   intended to convey any level of anonymity.

   Since the IMEI is permanently assigned to the mobile device and is
   not modified when the ownership of the mobile device changes (even
   upon a complete software reload of the device), the IMEI URN MUST NOT
   be used as a user identifier or user address by an application.
   Using the IMEI to identify a user or as a user address could result
   in communications destined for a previous owner of a device being
   received by the new device owner or could allow the new device owner
   to access information or services owned by the previous device owner.

   Additionally, since the IMEI identifies the mobile device, it
   potentially could be used to identify and track users for the
   purposes of surveillance and call data mining if sent in the clear.

   Since the IMEI is personally identifiable information, uses of the
   IMEI URN with IETF protocols require a specification and IETF Expert
   Review [14] in order to ensure that privacy concerns are
   appropriately addressed.  Protocols carrying the IMEI URN SHOULD at a
   minimum use channels that are strongly hop-by-hop encrypted, and it
   is RECOMMENDED that end-to-end encryption be used.

   Additional security considerations are specified in 3GPP TS 22.016
   [9].  Specifically, the IMEI is to be incorporated in a module that
   is contained within the terminal.  The IMEI SHALL NOT be changed
   after the terminal's production process.  It SHALL resist tampering,
   i.e., manipulation and change, by any means (e.g., physical,
   electrical, and software).

9.  Acknowledgements

   This document draws heavily on the 3GPP work on Numbering,
   Addressing, and Identification in 3GPP TS 23.003 [2] and also on the
   style and structure used in RFC 4122 [12].  The authors would like to
   thank Cullen Jennings, Lisa Dusseault, Dale Worley, Ivo Sedlacek,
   Atle Monrad, James Yu, Mary Barnes, Tim Bray, S. Moonesamy, Alexey
   Melnikov, Martin Duerst, John Klensin, Paul Kyzivat, Christer
   Holmberg, Barry Leiba, and Stephen Farrell for their help and
   comments.

10.  References

10.1.  Normative References

   [1]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
        "Uniform Resource Names (URN) Namespace Definition Mechanisms",
        BCP 66, RFC 3406, October 2002.

   [2]  3GPP, "Numbering, addressing and identification", 3GPP TS 23.003
        (Release 8), March 2014, <ftp://ftp.3gpp.org/Specs/
        archive/23_series/23.003/>.

   [3]  GSM 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>.

   [4]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [5]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [6]  3GPP, "Mobile radio interface Layer 3 specification; Core
        network protocols; Stage 3", 3GPP TS 24.008 (Release 8), June
        2013, <ftp://ftp.3gpp.org/Specs/archive/24_series/ 24.008/>.

   [7]  Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
        63, RFC 3629, November 2003.

   [8]  Moats, R., "URN Syntax", RFC 2141, May 1997.

   [9]  3GPP, "International Mobile station Equipment Identities
        (IMEI)", 3GPP TS 22.016 (Release 8), December 2009,
        <ftp://ftp.3gpp.org/Specs/archive/22_series/22.016/>.

10.2.  Informative References

   [10] Allen, A., Ed., "Using the International Mobile station
        Equipment Identity (IMEI) Uniform Resource Name (URN) as an
        Instance ID", RFC 7255, May 2014.

   [11] Jennings, C., Mahy, R., and F. Audet, "Managing Client-
        Initiated Connections in the Session Initiation Protocol (SIP)",
        RFC 5626, October 2009.

   [12] Leach, P., Mealling, M., and R. Salz, "A Universally Unique
        IDentifier (UUID) URN Namespace", RFC 4122, July 2005.

   [13] 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.

   [14] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.

Authors' Addresses

   Michael Montemurro (editor)
   Blackberry
   4701 Tahoe Dr.
   Mississauga, Ontario  L4W 0B4
   Canada

   EMail: mmontemurro@blackberry.com


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

   EMail: aallen@blackberry.com


   David McDonald
   Eircom

   EMail: David.McDonald@meteor.ie


   Paul Gosden
   GSM Association
   1st Floor, Mid City Place, 71 High Holborn
   London
   England

   EMail: pgosden@gsma.com