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
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This Internet-Draft will expire on August 12, 2013.
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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 . . . . . . . . . . . . . . . . . . . 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
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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-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].
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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-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
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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. 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).
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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
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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,
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.
[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
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