Next-Generation Pan-European eCall
RFC 8147
| Document | Type | RFC - Proposed Standard (May 2017; No errata) | |
|---|---|---|---|
| Authors | Randall Gellens , Hannes Tschofenig | ||
| Last updated | 2018-12-20 | ||
| Replaces | draft-gellens-ecrit-ecall, draft-gellens-ecrit-ecall | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Allison Mankin | ||
| Shepherd write-up | Show (last changed 2016-11-13) | ||
| IESG | IESG state | RFC 8147 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Alissa Cooper | ||
| Send notices to | "Allison Mankin" <allison.mankin@gmail.com> | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | RFC-Ed-Ack | ||
Internet Engineering Task Force (IETF) R. Gellens
Request for Comments: 8147 Core Technology Consulting
Category: Standards Track H. Tschofenig
ISSN: 2070-1721 Individual
May 2017
Next-Generation Pan-European eCall
Abstract
This document describes how to use IP-based emergency services
mechanisms to support the next generation of the Pan-European in-
vehicle emergency call service defined under the eSafety initiative
of the European Commission (generally referred to as "eCall"). eCall
is a standardized and mandated system for a special form of emergency
calls placed by vehicles, providing real-time communications and an
integrated set of related data.
This document also registers MIME media types and an Emergency Call
Data Type for the eCall vehicle data and metadata/control data, and
an INFO package to enable carrying this data in SIP INFO requests.
Although this specification is designed to meet the requirements of
next-generation Pan-European eCall (NG-eCall), it is specified
generically such that the technology can be reused or extended to
suit requirements across jurisdictions.
Status of This Memo
This is an Internet Standards Track document.
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). Further information on
Internet Standards is available in Section 2 of RFC 7841.
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/rfc8147.
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Copyright Notice
Copyright (c) 2017 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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Gellens & Tschofenig Standards Track [Page 2]
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Document Scope . . . . . . . . . . . . . . . . . . . . . . . 6
4. eCall Requirements . . . . . . . . . . . . . . . . . . . . . 7
5. Vehicle Data . . . . . . . . . . . . . . . . . . . . . . . . 7
6. Data Transport . . . . . . . . . . . . . . . . . . . . . . . 7
7. Call Setup . . . . . . . . . . . . . . . . . . . . . . . . . 10
8. Test Calls . . . . . . . . . . . . . . . . . . . . . . . . . 11
9. The Metadata/Control Object . . . . . . . . . . . . . . . . . 11
9.1. The Control Block . . . . . . . . . . . . . . . . . . . . 13
9.1.1. The <ack> Element . . . . . . . . . . . . . . . . . . 14
9.1.1.1. Attributes of the <ack> Element . . . . . . . . . 14
9.1.1.2. Child Element of the <ack> Element . . . . . . . 15
9.1.1.3. Example of the <ack> Element . . . . . . . . . . 16
9.1.2. The <capabilities> Element . . . . . . . . . . . . . 16
9.1.2.1. Child Element of the <capabilities> Element . . . 16
9.1.2.2. Example of the <capabilities> Element . . . . . . 17
9.1.3. The <request> Element . . . . . . . . . . . . . . . . 17
9.1.3.1. Attributes of the <request> Element . . . . . . . 17
9.1.3.2. Child Element of the <request> Element . . . . . 19
9.1.3.3. Request Example . . . . . . . . . . . . . . . . . 19
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11. Security Considerations . . . . . . . . . . . . . . . . . . . 25
12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 27
13. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . 27
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
14.1. The EmergencyCallData Media Subtree . . . . . . . . . . 30
14.2. Service URN Registrations . . . . . . . . . . . . . . . 31
14.3. MIME Media Type Registration for
application/EmergencyCallData.eCall.MSD . . . . . . . . 31
14.4. MIME Media Type Registration for
application/EmergencyCallData.Control+xml . . . . . . . 32
14.5. Registration of the "eCall.MSD" Entry in the Emergency
Call Data Types Registry . . . . . . . . . . . . . . . . 34
14.6. Registration of the "Control" Entry in the Emergency
Call Data Types Registry . . . . . . . . . . . . . . . . 34
14.7. Registration for
urn:ietf:params:xml:ns:EmergencyCallData:control . . . . 34
14.8. Registry Creation . . . . . . . . . . . . . . . . . . . 35
14.8.1. Emergency Call Actions Registry . . . . . . . . . . 35
14.8.2. Emergency Call Action Failure Reasons Registry . . . 36
14.9. The EmergencyCallData.eCall.MSD INFO Package . . . . . . 37
14.9.1. Overall Description . . . . . . . . . . . . . . . . 37
14.9.2. Applicability . . . . . . . . . . . . . . . . . . . 37
14.9.3. INFO Package Name . . . . . . . . . . . . . . . . . 38
14.9.4. INFO Package Parameters . . . . . . . . . . . . . . 38
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14.9.5. SIP Option-Tags . . . . . . . . . . . . . . . . . . 38
14.9.6. INFO Request Body Parts . . . . . . . . . . . . . . 38
14.9.7. INFO Package Usage Restrictions . . . . . . . . . . 39
14.9.8. Rate of INFO Requests . . . . . . . . . . . . . . . 39
14.9.9. INFO Package Security Considerations . . . . . . . . 39
14.9.10. Implementation Details . . . . . . . . . . . . . . . 39
14.9.11. Examples . . . . . . . . . . . . . . . . . . . . . . 39
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
15.1. Normative References . . . . . . . . . . . . . . . . . . 40
15.2. Informative references . . . . . . . . . . . . . . . . . 41
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 42
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction
Emergency calls made from vehicles (e.g., in the event of a crash)
assist in significantly reducing road deaths and injuries by allowing
emergency services to be aware of the incident, the state (condition)
of the vehicle, and the location of the vehicle and to have a voice
communications channel with the vehicle occupants. This enables a
quick and appropriate response.
The European Commission initiative of eCall was conceived in the late
1990s and has evolved to a European Parliament decision requiring the
implementation of a compliant in-vehicle system (IVS) in new vehicles
and the deployment of eCall in the European Member States in the very
near future. Other regions are developing eCall-compatible systems.
The Pan-European eCall system is a standardized and mandated
mechanism for emergency calls by vehicles, providing a voice channel
and transmission of data. eCall establishes procedures for such
calls to be placed by in-vehicle systems, recognized and processed by
the mobile network, and routed to a specialized Public Safety
Answering Point (PSAP) where the vehicle data is available to assist
the call taker in assessing and responding to the situation. eCall
provides a standard set of vehicle, sensor (e.g., crash-related), and
location data.
An eCall can be either user initiated or automatically triggered.
Automatically triggered eCalls indicate a car crash or some other
serious incident. Manually triggered eCalls might be reports of
witnessed crashes or serious hazards, a request for medical
assistance, etc. PSAPs might apply specific operational handling to
manual and automatic eCalls.
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Legacy eCall is standardized (by 3GPP [SDO-3GPP] and the European
Committee for Standardization (CEN) [CEN]) as a 3GPP circuit-switched
call over Global System for Mobile communications (GSM) (2G) or
Universal Mobile Telecommunications System (UMTS) (3G). Flags in the
call setup mark the call as an eCall and further indicate if the call
was automatically or manually triggered. The call is routed to an
eCall-capable PSAP, a voice channel is established between the
vehicle and the PSAP, and an eCall in-band modem is used to carry a
defined set of vehicle, sensor (e.g., crash-related), and location
data (the Minimum Set of Data or MSD) within the voice channel. The
same in-band mechanism is used for the PSAP to acknowledge successful
receipt of the MSD and to request the vehicle to send a new MSD
(e.g., to check if the state of or location of the vehicle or its
occupants has changed). NG-eCall moves from circuit switched to
all-IP and carries the vehicle data and eCall signaling as additional
data carried with the call. This document describes how IETF
mechanisms for IP-based emergency calls (including [RFC6443] and
[RFC7852]) are used to provide the signaling and data exchange of the
next generation of Pan-European eCall.
The European Telecommunications Standards Institute (ETSI) [SDO-ETSI]
has published a Technical Report titled "Mobile Standards Group
(MSG); eCall for VoIP" [MSG_TR] that presents findings and
recommendations regarding support for eCall in an all-IP environment.
The recommendations include the use of 3GPP Internet Multimedia
System (IMS) emergency calling with additional elements identifying
the call as an eCall and as carrying eCall data and mechanisms for
carrying the data and eCall signaling. 3GPP IMS emergency services
support multimedia, providing the ability to carry voice, text, and
video. This capability is referred to within 3GPP as Multimedia
Emergency Services (MMES).
A transition period will exist during which time the various entities
involved in initiating and handling an eCall might support NG-eCall,
legacy eCall, or both. The issues of migration and co-existence
during the transition period are outside the scope of this document.
This document indicates how to use IP-based emergency services
mechanisms to support NG-eCall.
This document also registers MIME media types and Emergency Call Data
Types for the eCall vehicle data (MSD) and metadata/control data, and
an INFO package to enable carrying this data in SIP INFO requests.
The MSD is carried in the MIME type application/
EmergencyCallData.eCall.MSD and the metadata/control block is carried
in the MIME type application/EmergencyCallData.Control+xml (both of
which are registered in Section 14). An INFO package is defined (in
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Section 14.9) to enable these MIME types to be carried in SIP INFO
requests, per [RFC6086].
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 [RFC2119].
This document reuses terminology defined in Section 3 of [RFC5012].
Additionally, we use the following abbreviations:
3GPP: 3rd Generation Partnership Project
CEN: European Committee for Standardization
EENA: European Emergency Number Association
ESInet: Emergency Services IP network
IMS: IP Multimedia Subsystem
IVS: In-Vehicle System
MNO: Mobile Network Operator
MSD: Minimum Set of Data
PSAP: Public Safety Answering Point
3. Document Scope
This document is focused on the signaling, data exchange, and
protocol needs of NG-eCall (also referred to as packet-switched eCall
or all-IP eCall) within the SIP framework for emergency calls (as
described in [RFC6443] and [RFC6881]). eCall itself is specified by
3GPP and CEN, and these specifications include far greater scope than
is covered here.
The eCall service operates over cellular wireless communication, but
this document does not address cellular-specific details, nor client
domain selection (e.g., circuit-switched versus packet-switched).
All such aspects are the purview of their respective standards
bodies. The scope of this document is limited to eCall operating
within a SIP-based environment (e.g., 3GPP IMS Emergency Calling
[TS23.167]).
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Although this specification is designed to meet the requirements of
Pan-European NG-eCall, it is specified generically such that the
technology can be reused or extended to suit requirements across
jurisdictions (see, e.g., [RFC8148]), and extension points are
provided to facilitate this.
Note that vehicles designed for multiple regions might need to
support eCall and other Advanced Automatic Crash Notification (AACN)
systems (such as described in [RFC8148]), but this is out of scope of
this document.
4. eCall Requirements
eCall requirements are specified by CEN in [EN_16072] and by 3GPP in
[TS22.101], Section 10.7 and Annex A.27, and [TS24.229],
Section 4.7.6. Requirements specific to vehicle data are contained
in EN 15722 [MSD].
5. Vehicle Data
Pan-European eCall provides a standardized and mandated set of
vehicle-related data (including VIN, vehicle type, propulsion type,
current and optionally previous location coordinates, and the number
of occupants) known as the Minimum Set of Data (MSD). CEN has
specified this data in EN 15722 [MSD], along with both ASN.1 and XML
encodings. Both circuit-switched eCall and this document use the
ASN.1 PER encoding, which is specified in Annex A of EN 15722 [MSD]
(the XML encoding specified in Annex C is not used in this document,
per 3GPP [SDO-3GPP]).
This document registers the application/EmergencyCallData.eCall.MSD
MIME media type to enable the MSD to be carried in SIP. As an ASN.1
PER-encoded object, the data is binary and transported using binary
content transfer encoding within SIP messages. This document also
adds "eCall.MSD" to the "Emergency Call Data Types" registry to
enable the MSD to be recognized as such in a SIP-based eCall
emergency call. (See [RFC7852] for more information about the
registry and how it is used.)
See Section 6 for a discussion of how the MSD vehicle data is
conveyed in an NG-eCall.
6. Data Transport
[RFC7852] establishes a general mechanism for conveying blocks of
data within a SIP emergency call. This document makes use of that
mechanism to include vehicle data (the MSD; see Section 5) and
metadata/control information (see Section 9) within SIP messages.
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This document also registers an INFO package (in Section 14.9) to
enable eCall-related data blocks to be carried in SIP INFO requests
(per [RFC6086], new INFO usages require the definition of an INFO
package).
Note that if other data sets need to be transmitted in the future,
the appropriate signaling mechanism for such data needs to be
evaluated, including factors such as the size and frequency of such
data.
An IVS transmits an MSD (see Section 5) by encoding it per Annex A of
EN 15722 [MSD] and including it as a MIME body part within a SIP
message per [RFC7852]. The body part is identified by its MIME media
type (application/EmergencyCallData.eCall.MSD) in the Content-Type
header field of the body part. The body part is assigned a unique
identifier that is listed in a Content-ID header field in the body
part. The SIP message is marked as containing the MSD by adding (or
appending to) a Call-Info header field at the top level of the SIP
message. This Call-Info header field contains a Content Identifier
(CID) URL referencing the body part's unique identifier and a
"purpose" parameter identifying the data as the eCall MSD per the
entry in the "Emergency Call Data Types" registry; the "purpose"
parameter's value is "EmergencyCallData.eCall.MSD". Per [RFC6086],
an MSD is carried in a SIP INFO request by using the INFO package
defined in Section 14.9.
A PSAP or IVS transmits a metadata/control object (see Section 9) by
encoding it per the description in this document and including it
within a SIP message as a MIME body part per [RFC7852]. The body
part is identified by its MIME media type (application/
EmergencyCallData.Control+xml) in the Content-Type header field of
the body part. The body part is assigned a unique identifier, which
is listed in a Content-ID header field in the body part. The SIP
message is marked as containing the metadata/control object by adding
(or appending to) a Call-Info header field at the top level of the
SIP message. This Call-Info header field contains a CID URL
referencing the body part's unique identifier and a "purpose"
parameter identifying the data as an eCall metadata/control block per
the entry in the "Emergency Call Data Types" registry; the "purpose"
parameter's value is "EmergencyCallData.Control". Per [RFC6086], a
metadata/control object is carried in a SIP INFO request by using the
INFO package defined in Section 14.9.
An MSD or a metadata/control block is always enclosed in a multipart
body part (even if it would otherwise be the only body part in the
SIP message).
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A body part containing an MSD or metadata/control object has a
Content-Disposition header field value containing "By-Reference".
An IVS initiating an NG-eCall includes an MSD as a body part within
the initial INVITE and optionally also includes a metadata/control
object informing the PSAP of its capabilities as another body part.
The MSD body part (and metadata/control and Presence Information Data
Format Location Object (PIDF-LO) body parts, if included) have a
Content-Disposition header field with the value "By-Reference;
handling=optional". Specifying "handling=optional" prevents the SIP
INVITE request from being rejected if it is processed by a legacy
element (e.g., a gateway between SIP and circuit-switched
environments) that does not understand the MSD (or metadata/control
object or PIDF-LO).
The PSAP creates a metadata/control object acknowledging receipt of
the MSD and includes it as a body part within the SIP final response
to the SIP INVITE request per [RFC7852]. A metadata/control object
is not included in provisional (e.g., 180) responses.
A PSAP is able to reject a call while indicating that it is aware of
the situation by including a metadata/control object acknowledging
the MSD and containing "received=true" within a final response using
SIP response code 600 (Busy Everywhere), 486 (Busy Here), or 603
(Decline), per [RFC7852].
If the IVS receives an acknowledgment for an MSD containing
"received=false", this indicates that the PSAP was unable to properly
decode or process the MSD. The IVS action is not defined (e.g., it
might only log an error). Since the PSAP is able to request an
updated MSD during the call, if an initial MSD is unsatisfactory in
any way, the PSAP can choose to request another one.
A PSAP can request that the vehicle send an updated MSD during a call
(e.g., upon manual request of the PSAP call taker who suspects the
vehicle state may have changed). To do so, the PSAP creates a
metadata/control object requesting an MSD and includes it within a
SIP INFO request sent within the dialog. The IVS then includes an
updated MSD within a SIP INFO request and sends it within the dialog.
If the IVS is unable to send an MSD, it instead sends a metadata/
control object acknowledging the request, containing an
<actionResult> element with a "success" parameter set to "false" and
a "reason" parameter (and optionally a "details" parameter)
indicating why the request could not be accomplished. Per [RFC6086],
metadata/control objects and MSDs are sent using the INFO package
defined in Section 14.9. In addition, to align with how an MSD or
metadata/control block is transmitted in a SIP message other than an
INFO request, a Call-Info header field is included in the SIP INFO
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request to reference the MSD or metadata/control block per [RFC7852].
See Section 14.9 for information about the use of SIP INFO requests
to carry data within an eCall.
The IVS is not expected to send an unsolicited MSD after the initial
INVITE.
This document does not mandate support for the data blocks defined in
[RFC7852].
7. Call Setup
In a circuit-switched eCall, the IVS places a special form of a 112
emergency call, which carries an eCall flag (indicating that the call
is an eCall and also if the call was manually or automatically
triggered); the mobile network operator (MNO) recognizes the eCall
flag and routes the call to an eCall-capable PSAP, and vehicle data
is transmitted to the PSAP via the eCall in-band modem (in the voice
channel).
///-----\\\ 112 voice call with eCall flag +------+
||| IVS |||---------------------------------------->| PSAP |
\\\-----/// vehicle data via eCall in-band modem +------+
Figure 1: Circuit-Switched eCall
For NG-eCall, the IVS establishes an emergency call using a Request-
URI indicating a manual or automatic eCall; the MNO (or ESInet)
recognizes the eCall URN and routes the call to an NG-eCall-capable
PSAP; and the PSAP interprets the vehicle data sent with the call and
makes it available to the call taker.
///-----\\\ IMS emergency call with eCall URN +------+
||| IVS |||---------------------------------------->| PSAP |
\\\-----/// vehicle data included in call setup +------+
Figure 2: NG-eCall
See Section 6 for information on how the MSD is transported within an
NG-eCall.
This document adds new service URN children within the "sos"
subservice. These URNs provide the mechanism by which an eCall is
identified and differentiate between manually and automatically
triggered eCalls (which might be subject to different treatment,
depending on policy). The two service URNs are:
urn:service:sos.ecall.automatic and urn:service:sos.ecall.manual,
which request resources associated with an emergency call placed by
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an in-vehicle system, carrying a standardized set of data related to
the vehicle and incident. These are registered in Section 14.2.
Call routing is outside the scope of this document.
8. Test Calls
eCall requires the ability to place test calls (see [TS22.101],
clause 10.7 and [EN_16062], clause 7.2.2). These are calls that are
recognized and treated to some extent as eCalls but are not given
emergency call treatment and are not handled by call takers. The
specific handling of test eCalls is outside the scope of this
document; typically, the test call facility allows the IVS or user to
verify that an eCall can be successfully established with voice
communication. The IVS might also be able to verify that the MSD was
successfully received.
A service URN starting with "test." indicates a test call. For
eCall, "urn:service:test.sos.ecall" indicates such a test feature.
The "test" service URN is defined in [RFC6881].
This document specifies "urn:service:test.sos.ecall" for eCall test
calls. This is registered in Section 14.2.
The circuit-switched eCall test call facility is a non-emergency
number, so it does not get treated as an emergency call. For
NG-eCall, MNOs, emergency authorities, and PSAPs can determine how to
treat a vehicle call requesting the "test" service URN so that the
desired functionality is tested, but this is outside the scope of
this document.
9. The Metadata/Control Object
eCall requires the ability for the PSAP to acknowledge successful
receipt of an MSD sent by the IVS and for the PSAP to request that
the IVS send an MSD (e.g., the call taker can initiate a request for
a new MSD to see if there have been changes in the vehicle's state,
such as location, direction, or number of fastened seat belts).
This document defines a block of metadata/control data as an XML
structure containing elements used for eCall and other related
emergency call systems and extension points. (This metadata/control
block is in effect a high-level protocol between the PSAP and IVS.)
This document registers the application/EmergencyCallData.Control+xml
MIME media type to enable the metadata/control data to be carried in
SIP. This document also adds "Control" to the "Emergency Call Data
Types" registry to enable the metadata/control block to be recognized
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as such in a SIP-based eCall emergency call. (See [RFC7852] for more
information about the registry and how it is used.)
See Section 6 for a discussion of how the metadata/control data is
conveyed in an NG-eCall.
When the PSAP sends a metadata/control block in response to data sent
by the IVS in a SIP request other than INFO (e.g., the MSD in the
initial INVITE), the metadata/control block is sent in the SIP
response to that request (e.g., the response to the INVITE request).
When the PSAP sends a control block in other circumstances (e.g., mid
call), the control block is transmitted from the PSAP to the IVS in a
SIP INFO request within the established dialog. The IVS sends the
requested data (the MSD) in a new SIP INFO request (per [RFC6086]).
This mechanism flexibly allows the PSAP to send eCall-specific data
to the IVS and the IVS to respond. SIP INFO requests are sent using
an appropriate INFO package. See Section 6 for more information on
sending a metadata/control block within a SIP message. See
Section 14.9 for information about the use of SIP INFO requests to
carry data within an eCall.
When the IVS includes an unsolicited MSD in a SIP request (e.g., the
initial INVITE), the PSAP sends a metadata/control block indicating
successful/unsuccessful receipt of the MSD in the SIP response to the
request. This also informs the IVS that an NG-eCall is in operation.
If the IVS receives a SIP final response without the metadata/control
block, it indicates that the SIP dialog is not an NG-eCall (e.g.,
some part of the call is being handled as a legacy call). When the
IVS sends a solicited MSD (e.g., in a SIP INFO request sent following
receipt of a SIP INFO request containing a metadata/control block
requesting an MSD), the PSAP does not send a metadata/control block
indicating successful or unsuccessful receipt of the MSD. (Normal
SIP retransmission handles non-receipt of requested data; note that,
per [RFC6086], a 200 OK response to a SIP INFO request indicates only
that the receiver has successfully received and accepted the SIP INFO
request, and it says nothing about the acceptability of the payload.)
If the IVS receives a request to send an MSD but it is unable to do
so for any reason, the IVS instead sends a metadata/control object
acknowledging the request, containing an <actionResult> element with
a "success" parameter set to "false" and a "reason" parameter (and
optionally a "details" parameter) indicating why the request could
not be accomplished.
This provides flexibility to handle various circumstances. For
example, if a PSAP is unable to accept an eCall (e.g., due to
overload or too many calls from the same location), it can reject the
INVITE. Since a metadata/control object is also included in the SIP
response that rejects the call, the IVS knows if the PSAP received
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the MSD and can inform the vehicle occupants that the PSAP
successfully received the vehicle location and information but can't
talk to the occupants at that time. Especially for SIP response
codes that indicate an inability to conduct a call (as opposed to a
technical inability to process the request), the IVS can also
determine that the call was successful on a technical level (e.g.,
not helpful to retry as circuit switched). (Note that there could be
edge cases where the PSAP response is not received by the IVS, e.g.,
if an intermediary sends a CANCEL, and an error response is forwarded
towards the IVS before the error response from the PSAP is received,
the response will be dropped, but these are unlikely to occur here.)
The metadata/control block is carried in the MIME type application/
EmergencyCallData.Control+xml.
The metadata/control block is designed for use with Pan-European
eCall and also eCall-like systems (i.e., in other regions), and it
has extension points. Note that eCall-like systems might define
their own vehicle data blocks and might need to register a new INFO
package to accommodate the new data MIME media type and the metadata/
control object.
9.1. The Control Block
The control block is an XML data structure allowing for
acknowledgments, requests, and capabilities information. It is
carried in a body part with a specific MIME media type. Three
elements are defined for use within a control block:
ack Acknowledges receipt of data or a request.
capabilities Used in a control block sent from the IVS to the PSAP
(e.g., in the initial INVITE) to inform the PSAP of the
vehicle capabilities. Child elements contain all
actions and data types supported by the vehicle. It is
OPTIONAL for the IVS to send this block. Omitting the
block indicates that the IVS supports only the
mandatory functionality defined in this document.
request Used in a control block sent by the PSAP to the IVS to
request the vehicle to perform an action.
The <ack> element indicates the object being acknowledged and reports
success or failure.
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The <request> element contains attributes to indicate the request and
to supply related information. The "action" attribute is mandatory
and indicates the specific action. An IANA registry is created in
Section 14.8.1 to contain the allowed values.
The <capabilities> element has child <request> elements to indicate
the actions supported by the IVS.
9.1.1. The <ack> Element
The <ack> element acknowledges receipt of an eCall data object or
request. An <ack> element references the Content-ID of the object
being acknowledged. The PSAP MUST send an <ack> element
acknowledging receipt of an unsolicited MSD (e.g., sent by the IVS in
the INVITE); this <ack> element indicates if the PSAP considers the
MSD successfully received or not. An <ack> element is not sent for a
<capabilities> element.
9.1.1.1. Attributes of the <ack> Element
The <ack> element has the following attributes:
Name: ref
Usage: Mandatory
Type: anyURI
Direction: Sent in either direction
Description: References the Content-ID of the body part being
acknowledged.
Example: <ack received="true"
ref="1234567890@atlanta.example.com"/>
Name: received
Usage: Conditional: mandatory in an <ack> element sent by a
PSAP
Type: boolean
Direction: In this document, sent from the PSAP to the IVS
Description: Indicates if the referenced object was considered
successfully received or not.
Example: <ack received="true"
ref="1234567890@atlanta.example.com"/>
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9.1.1.2. Child Element of the <ack> Element
For extensibility, the <ack> element has the following child element:
Name: actionResult
Usage: Optional
Direction: Sent from the IVS to the PSAP
Description: An <actionResult> element indicates the result of an
action (other than a successfully executed "send-data" action).
The <ack> element contains an <actionResult> element for each
<request> element that is not a successfully executed "send-data"
action. The <actionResult> element has the following attributes:
Name: action
Usage: Mandatory
Type: token
Description: Contains the value of the "action" attribute of the
<request> element
Name: success
Usage: Mandatory
Type: boolean
Description: Indicates if the action was successfully
accomplished
Name: reason
Usage: Conditional
Type: token
Description: Used when "success" is "false", this attribute
contains a reason code for a failure. A registry for reason
codes is defined in Section 14.8.2. The initial values are:
damaged (required components are damaged), data-unsupported
(the data item referenced in a "send-data" request is not
supported), security-failure (the authenticity of the request
or the authority of the requestor could not be verified),
unable (a generic error for use when no other code is
appropriate), and unsupported (the "action" value is not
supported).
Name: details
Usage: optional
Type: string
Description: Contains further explanation of the circumstances of
a success or failure. The contents are implementation specific
and human readable. This is intended for internal use and
troubleshooting, not for display to vehicle occupants.
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9.1.1.3. Example of the <ack> Element
<?xml version="1.0" encoding="UTF-8"?>
<EmergencyCallData.Control
xmlns="urn:ietf:params:xml:ns:EmergencyCallData:control"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<ack received="true" ref="1234567890@atlanta.example.com"/>
</EmergencyCallData.Control>
Figure 3: <ack> Example from PSAP to IVS
9.1.2. The <capabilities> Element
The <capabilities> element is transmitted by the IVS to indicate its
capabilities to the PSAP. No attributes for this element are
currently defined. There is one child element defined.
9.1.2.1. Child Element of the <capabilities> Element
The <capabilities> element has the following child element:
Name: request
Usage: Mandatory
Description: The <capabilities> element contains a <request> child
element per action supported by the vehicle.
Example:
<capabilities>
<request action="send-data" supported-values="eCall.MSD" />
</capabilities>
It is OPTIONAL for the IVS to support the <capabilities> element. If
the IVS does not send a <capabilities> element, this indicates that
the only <request> action supported by the IVS is "send-data" with
"datatype" set to "eCall.MSD".
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9.1.2.2. Example of the <capabilities> Element
<?xml version="1.0" encoding="UTF-8"?>
<EmergencyCallData.Control
xmlns="urn:ietf:params:xml:ns:EmergencyCallData:control">
<capabilities>
<request action="send-data" supported-values="eCall.MSD"/>
</capabilities>
</EmergencyCallData.Control>
Figure 4: <capabilities> Element Example
9.1.3. The <request> Element
A <request> element appears one or more times on its own or as a
child of a <capabilities> element. It allows the PSAP to request
that the IVS perform an action. The only action that MUST be
supported is to send an MSD. The attributes and child elements are
defined as follows.
9.1.3.1. Attributes of the <request> Element
The <request> element has the following attributes:
Name: action
Usage: Mandatory
Type: token
Direction: Sent in either direction
Description: Identifies the action that the vehicle is requested to
perform (in a <request> element within a <capabilities> element;
indicates an action that the vehicle is capable of performing).
An IANA registry is established in Section 14.8.1 to contain the
allowed values.
Example: action="send-data"
Name: int-id
Usage: Conditional
Type: unsignedInt
Direction: Sent in either direction
Description: Defined for extensibility. Documents that make use of
it are expected to explain when it is required and how it is used.
Example: int-id="3"
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Name: persistence
Usage: Optional
Type: duration
Direction: Sent in either direction
Description: Defined for extensibility. Specifies how long to carry
on the specified action. If absent, the default is for the
duration of the call.
Example: persistence="PT1H"
Name: datatype
Usage: Conditional
Type: token
Direction: Sent in either direction
Description: Mandatory with a "send-data" action within a <request>
element that is not within a <capabilities> element. Specifies
the data block that the IVS is requested to transmit, using the
same identifier as in the "purpose" attribute set in a Call-Info
header field to point to the data block. Permitted values are
contained in IANA's "Emergency Call Data Types" registry
established in [RFC7852]. Only the "eCall.MSD" value is mandatory
to support.
Example: datatype="eCall.MSD"
Name: supported-values
Usage: Conditional
Type: string
Direction: Sent from the IVS to the PSAP
Description: Defined for extensibility. Used in a <request> element
that is a child of a <capability> element, this attribute lists
all supported values of the action type. Permitted values depend
on the action value. Multiple values are separated with a
semicolon. White space is ignored. Documents that make use of it
are expected to explain when it is required, the permitted values,
and how it is used.
Name: requested-state
Usage: Conditional
Type: token
Direction: Sent from the PSAP to the IVS
Description: Defined for extension. Indicates the requested state
of an element associated with the request type. Permitted values
depend on the request type. Documents that make use of it are
expected to explain when it is required, the permitted values, and
how it is used.
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Name: element-id
Usage: Conditional
Type: token
Direction: Sent from the PSAP to the IVS
Description: Defined for extension. Identifies the element to be
acted on. Permitted values depend on the request type. Documents
that make use of it are expected to explain when it is required,
the permitted values, and how it is used.
9.1.3.2. Child Element of the <request> Element
For extensibility, the <request> element has the following child
element:
Name: text
Usage: Optional
Type: string
Direction: Sent from the PSAP to the IVS
Description: Defined for extension.
9.1.3.3. Request Example
<?xml version="1.0" encoding="UTF-8"?>
<EmergencyCallData.Control
xmlns="urn:ietf:params:xml:ns:EmergencyCallData:control">
<request action="send-data" datatype="eCall.MSD"/>
</EmergencyCallData.Control>
Figure 5: <request> Element Example
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10. Examples
Figure 6 illustrates an eCall. The call uses the request URI
urn:service:sos.ecall.automatic service URN and is recognized as an
eCall, and further as one that was invoked automatically by the IVS
due to a crash or other serious incident. In this example, the
originating network routes the call to an ESInet, which routes the
call to the appropriate NG-eCall-capable PSAP. The emergency call is
received by the ESInet's Emergency Services Routing Proxy (ESRP), as
the entry point into the ESInet. The ESRP routes the call to a PSAP,
where it is received by a call taker. In deployments where there is
no ESInet, the originating network routes the call directly to the
appropriate NG-eCall-capable PSAP, an illustration of which would be
identical to the one below except without an ESInet or ESRP.
+-----------+ +----------------------------------------+
| | | +-------+ |
| | | | PSAP2 | |
| | | +-------+ |
| | | |
| | | +------+ +----------------------+ |
Vehicle-->| |--|-->| ESRP |-->| PSAP1 --> Call Taker | |
| | | +------+ +----------------------+ |
| | | |
| | | +-------+ |
| | | | PSAP3 | |
|Originating| | +-------+ |
| Mobile | | |
| Network | | ESInet |
+-----------+ +----------------------------------------+
Figure 6: Example of NG-eCall Message Flow
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Figure 7 illustrates an eCall call flow with a mid-call PSAP request
for an updated MSD. The call flow shows the IVS initiating an
emergency call, including the MSD in the INVITE. The PSAP includes
in the 200 OK response a metadata/control object acknowledging
receipt of the MSD. During the call, the PSAP sends a request for an
MSD in an INFO request. The IVS sends the requested MSD in a new
INFO request.
IVS PSAP
|(1) INVITE (eCall MSD) |
|------------------------------------------->|
| |
|(2) 200 OK (eCall metadata [ack MSD]) |
|<-------------------------------------------|
| |
|(3) start media stream(s) |
|............................................|
| |
|(4) INFO (eCall metadata [request MSD]) |
|<-------------------------------------------|
| |
|(5) 200 OK |
|------------------------------------------->|
| |
|(6) INFO (eCall MSD) |
|------------------------------------------->|
| |
|(7) 200 OK |
|<-------------------------------------------|
| |
|(8) BYE |
|<-------------------------------------------|
| |
|(9) end media streams |
|............................................|
| |
|(10) 200 OK |
|------------------------------------------->|
Figure 7: NG-eCall Call Flow Illustration
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Figure 8 illustrates a SIP eCall INVITE request containing an MSD.
For simplicity, the example does not show all SIP headers, nor the
Session Description Protocol (SDP) contents, nor does it show any
additional data blocks added by the IVS or the originating mobile
network. Because the MSD is encoded in ASN.1 PER, which is a binary
encoding, its contents cannot be included in a text document.
INVITE urn:service:sos.ecall.automatic SIP/2.0
To: urn:service:sos.ecall.automatic
From: <sip:+13145551111@example.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.example.com
Geolocation: <cid:target123@example.com>
Geolocation-Routing: no
Call-Info: <cid:1234567890@atlanta.example.com>;
purpose=EmergencyCallData.eCall.MSD
Accept: application/sdp, application/pidf+xml,
application/EmergencyCallData.Control+xml
CSeq: 31862 INVITE
Recv-Info: EmergencyCallData.eCall.MSD
Allow: INVITE, ACK, PRACK, INFO, OPTIONS, CANCEL, REFER, BYE,
SUBSCRIBE, NOTIFY, UPDATE
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/sdp
...Session Description Protocol (SDP) goes here...
--boundary1
Content-Type: application/pidf+xml
Content-ID: <target123@example.com>
Content-Disposition: by-reference;handling=optional
...PIDF-LO goes here...
--boundary1
Content-Type: application/EmergencyCallData.eCall.MSD
Content-ID: <1234567890@atlanta.example.com>
Content-Disposition: by-reference;handling=optional
...MSD in ASN.1 PER encoding goes here...
--boundary1--
Figure 8: SIP NG-eCall INVITE
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Continuing the example, Figure 9 illustrates a SIP 200 OK response to
the INVITE request of Figure 8, containing a metadata/control block
acknowledging successful receipt of the eCall MSD. (For simplicity,
the example does not show all SIP headers.)
SIP/2.0 200 OK
To: urn:service:sos.ecall.automatic;tag=8gydfe65t0
From: <sip:+13145551111@example.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.example.com
Call-Info: <cid:2345678901@atlanta.example.com>;
purpose=EmergencyCallData.Control
Accept: application/sdp, application/pidf+xml,
application/EmergencyCallData.Control+xml,
application/EmergencyCallData.eCall.MSD
CSeq: 31862 INVITE
Recv-Info: EmergencyCallData.eCall.MSD
Allow: INVITE, ACK, PRACK, INFO, OPTIONS, CANCEL, REFER, BYE,
SUBSCRIBE, NOTIFY, UPDATE
Content-Type: multipart/mixed; boundary=boundaryX
Content-Length: ...
--boundaryX
Content-Type: application/sdp
...Session Description Protocol (SDP) goes here...
--boundaryX
Content-Type: application/EmergencyCallData.Control+xml
Content-ID: <2345678901@atlanta.example.com>
Content-Disposition: by-reference
<?xml version="1.0" encoding="UTF-8"?>
<EmergencyCallData.Control
xmlns="urn:ietf:params:xml:ns:EmergencyCallData:control">
<ack received="true" ref="1234567890@atlanta.example.com"/>
</EmergencyCallData.Control>
--boundaryX--
Figure 9: 200 OK Response to INVITE
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Figure 10 illustrates a SIP INFO request containing a metadata/
control block requesting an eCall MSD. (For simplicity, the example
does not show all SIP headers.)
INFO sip:+13145551111@example.com SIP/2.0
To: <sip:+13145551111@example.com>;tag=9fxced76sl
From: Exemplar PSAP <urn:service:sos.ecall.automatic>;tag=8gydfe65t0
Call-ID: 3848276298220188511@atlanta.example.com
Call-Info: <cid:3456789012@atlanta.example.com>;
purpose=EmergencyCallData.Control
CSeq: 41862 INFO
Info-Package: EmergencyCallData.eCall.MSD
Allow: INVITE, ACK, PRACK, INFO, OPTIONS, CANCEL, REFER, BYE,
SUBSCRIBE, NOTIFY, UPDATE
Content-Type: multipart/mixed; boundary=boundaryZZZ
Content-Disposition: Info-Package
Content-Length: ...
--boundaryZZZ
Content-Disposition: by-reference
Content-Type: application/EmergencyCallData.Control+xml
Content-ID: <3456789012@atlanta.example.com>
<?xml version="1.0" encoding="UTF-8"?>
<EmergencyCallData.Control
xmlns="urn:ietf:params:xml:ns:EmergencyCallData:control">
<request action="send-data" datatype="eCall.MSD"/>
</EmergencyCallData.Control>
--boundaryZZZ--
Figure 10: INFO Requesting MSD
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Figure 11 illustrates a SIP INFO request containing an MSD. For
simplicity, the example does not show all SIP headers. Because the
MSD is encoded in ASN.1 PER, which is a binary encoding, its contents
cannot be included in a text document.
INFO urn:service:sos.ecall.automatic SIP/2.0
To: urn:service:sos.ecall.automatic;tag=8gydfe65t0
From: <sip:+13145551111@example.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.example.com
Call-Info: <cid:4567890123@atlanta.example.com>;
purpose=EmergencyCallData.eCall.MSD
CSeq: 51862 INFO
Info-Package: EmergencyCallData.eCall.MSD
Allow: INVITE, ACK, PRACK, INFO, OPTIONS, CANCEL, REFER, BYE,
SUBSCRIBE, NOTIFY, UPDATE
Content-Type: multipart/mixed; boundary=boundaryLine
Content-Disposition: Info-Package
Content-Length: ...
--boundaryLine
Content-Type: application/EmergencyCallData.eCall.MSD
Content-ID: <4567890123@atlanta.example.com>
Content-Disposition: by-reference
...MSD in ASN.1 PER encoding goes here...
--boundaryLine--
Figure 11: INFO Containing MSD
11. Security Considerations
The security considerations described in [RFC5069] (on marking and
routing emergency calls) apply here.
In addition to any network-provided location (which might be
determined solely by the network or in cooperation with or possibly
entirely by the originating device), an eCall carries an IVS-supplied
location within the MSD. This is likely to be useful to the PSAP,
especially when no network-provided location is included, or when the
two locations are independently determined. Even in situations where
the network-supplied location is limited to the cell site, this can
be useful as a sanity check on the device-supplied location contained
in the MSD.
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The document [RFC7378] discusses trust issues regarding location
provided by or determined in cooperation with end devices.
Security considerations specific to the mechanism by which the PSAP
sends acknowledgments and requests to the vehicle are discussed in
the "Security Considerations" block of Section 14.4. Note that an
attacker that has access to and is capable of generating a response
to the initial INVITE request could generate a 600 (Busy Everywhere),
486 (Busy Here), or 603 (Decline) response that includes a metadata/
control object containing a reference to the MSD in the initial
INVITE and a "received=true" field, which could result in the IVS
perceiving the PSAP to be overloaded and hence not attempting to
reinitiate the call. The risk can be mitigated as discussed in the
"Security Considerations" block of Section 14.4.
Data received from external sources inherently carries implementation
risks. For example, depending on the platform, buffer overflows can
introduce remote code execution vulnerabilities, null characters can
corrupt strings, numeric values used for internal calculations can
result in underflow/overflow errors, malformed XML objects can expose
parsing bugs, etc. Implementations need to be cognizant of the
potential risks, observe best practices (which might include
sufficiently capable static code analysis, fuzz testing, component
isolation, avoiding use of unsafe coding techniques, third-party
attack tests, signed software, over-the-air updates, etc.), and have
multiple levels of protection. Implementors need to be aware that,
potentially, the data objects described here and elsewhere (including
the MSD and metadata/control objects) might be malformed, contain
unexpected characters, have excessively long attribute values and
elements, etc.
The security considerations discussed in [RFC7852] apply here (see
especially the discussion of Transport Layer Security (TLS), TLS
versions, cipher suites, and PKI).
When vehicle data or control/metadata is contained in a signed or
encrypted body part, the enclosing multipart (e.g., multipart/signed
or multipart/encrypted) has the same Content-ID as the enclosed data
part. This allows an entity to identify and access the data blocks
it is interested in without having to dive deeply into the message
structure or decrypt parts it is not interested in. (The "purpose"
parameter in a Call-Info header field identifies the data and
contains a CID URL pointing to the data block in the body, which has
a matching Content-ID body part header field.)
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12. Privacy Considerations
The privacy considerations discussed in [RFC7852] apply here. The
MSD carries some identifying and personal information (mostly about
the vehicle and less about the owner), as well as location
information, so it needs to be protected against unauthorized
disclosure. Local regulations may impose additional privacy
protection requirements.
Privacy considerations specific to the data structure containing
vehicle information are discussed in the "Security Considerations"
block of Section 14.3.
Privacy considerations specific to the mechanism by which the PSAP
sends acknowledgments and requests to the vehicle are discussed in
the "Security Considerations" block of Section 14.4.
13. XML Schema
This section defines an XML schema for the control block. The text
description of the control block in Section 9.1 is normative and
supersedes any conflicting aspect of this schema.
<?xml version="1.0"?>
<xs:schema
targetNamespace="urn:ietf:params:xml:ns:EmergencyCallData:control"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:pi="urn:ietf:params:xml:ns:EmergencyCallData:control"
xmlns:xml="http://www.w3.org/XML/1998/namespace"
elementFormDefault="qualified"
attributeFormDefault="unqualified">
<xs:import namespace="http://www.w3.org/XML/1998/namespace"/>
<xs:element name="EmergencyCallData.Control"
type="pi:controlType"/>
<xs:complexType name="controlType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:choice>
<xs:element name="capabilities"
type="pi:capabilitiesType"/>
<xs:element name="request" type="pi:requestType"/>
<xs:element name="ack" type="pi:ackType"/>
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<xs:any namespace="##any" processContents="lax"
minOccurs="0"
maxOccurs="unbounded"/>
</xs:choice>
<xs:anyAttribute/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="ackType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence minOccurs="1" maxOccurs="unbounded">
<xs:element name="actionResult" minOccurs="0"
maxOccurs="unbounded">
<xs:complexType>
<xs:attribute name="action"
type="xs:token"
use="required"/>
<xs:attribute name="success"
type="xs:boolean"
use="required"/>
<xs:attribute name="reason"
type="xs:token">
<xs:annotation>
<xs:documentation>
conditionally mandatory
when @success="false"
to indicate reason code
for a failure
</xs:documentation>
</xs:annotation>
</xs:attribute>
<xs:attribute name="details"
type="xs:string"/>
<xs:anyAttribute
processContents="skip"/>
</xs:complexType>
</xs:element>
<xs:any namespace="##any" processContents="lax"
minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="ref"
type="xs:anyURI"
use="required"/>
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<xs:attribute name="received"
type="xs:boolean"/>
<xs:anyAttribute/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="capabilitiesType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:sequence minOccurs="1" maxOccurs="unbounded">
<xs:element name="request"
type="pi:requestType"
minOccurs="1"
maxOccurs="unbounded"/>
<xs:any namespace="##any" processContents="lax"
minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:anyAttribute/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
<xs:complexType name="requestType">
<xs:complexContent>
<xs:restriction base="xs:anyType">
<xs:choice minOccurs="1" maxOccurs="unbounded">
<xs:element name="text" minOccurs="0"
maxOccurs="unbounded">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:anyAttribute
namespace="##any"
processContents="skip"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:any namespace="##any" processContents="lax"
minOccurs="0"
maxOccurs="unbounded"/>
</xs:choice>
<xs:attribute name="action" type="xs:token"
use="required"/>
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<xs:attribute name="int-id" type="xs:unsignedInt"/>
<xs:attribute name="persistence"
type="xs:duration"/>
<xs:attribute name="datatype" type="xs:token"/>
<xs:attribute name="supported-values"
type="xs:string"/>
<xs:attribute name="element-id" type="xs:token"/>
<xs:attribute name="requested-state"
type="xs:token"/>
<xs:anyAttribute/>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
</xs:schema>
Figure 12: Control Block Schema
14. IANA Considerations
14.1. The EmergencyCallData Media Subtree
This document establishes the "EmergencyCallData" media (MIME)
subtype tree, a new media subtree rooted at "application/
EmergencyCallData". This subtree is used only for content associated
with emergency communications. New subtypes in this subtree follow
the rules specified in Section 3.1 of [RFC6838], with the additional
restriction that the standards-related organization MUST be
responsible for some aspect of emergency communications.
This subtree initially contains the following subtypes (defined here
or in [RFC7852]):
EmergencyCallData.Comment+xml
EmergencyCallData.Control+xml
EmergencyCallData.DeviceInfo+xml
EmergencyCallData.eCall.MSD
EmergencyCallData.ProviderInfo+xml
EmergencyCallData.ServiceInfo+xml
EmergencyCallData.SubscriberInfo+xml
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14.2. Service URN Registrations
IANA has registered the URN urn:service:sos.ecall under the "'sos'
Sub-Services" registry defined in Section 4.2 of [RFC5031].
This service requests resources associated with an emergency call
placed by an in-vehicle system, carrying a standardized set of data
related to the vehicle and incident. The "Description" registry
field is "Vehicle-initiated emergency calls". Two sub-services are
registered as well:
urn:service:sos.ecall.automatic
Used with an eCall invoked automatically, for example, due to a
crash or other serious incident. The "Description" registry field
is "Automatic vehicle-initiated emergency calls".
urn:service:sos.ecall.manual
Used with an eCall invoked due to manual interaction by a vehicle
occupant. The "Description" registry field is "Manual vehicle-
initiated emergency calls".
IANA has also registered the URN urn:service:test.sos.ecall under the
"'test' Sub-Services" registry defined in Section 17.2 of [RFC6881].
This service requests resources associated with a test (non-
emergency) call placed by an in-vehicle system. See Section 8 for
more information on the test eCall request URN.
14.3. MIME Media Type Registration for application/
EmergencyCallData.eCall.MSD
IANA has added application/EmergencyCallData.eCall.MSD as a MIME
media type, with a reference to this document, in accordance with the
procedures of RFC 6838 [RFC6838] and guidelines in RFC 7303
[RFC7303].
MIME media type name: application
MIME subtype name: EmergencyCallData.eCall.MSD
Mandatory parameters: none
Optional parameters: none
Encoding scheme: binary
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Encoding considerations:
Uses ASN.1 PER, which is a binary encoding; when transported in
SIP, binary content transfer encoding is used.
Security considerations:
This media type is designed to carry vehicle and incident-
related data during an emergency call. This data contains
personal information including vehicle VIN, location,
direction, etc. Appropriate precautions need to be taken to
limit unauthorized access, inappropriate disclosure to third
parties, and eavesdropping of this information. Sections 9 and
10 of [RFC7852] contain more discussion.
Interoperability considerations: None
Published specification: Annex A of EN 15722 [MSD]
Applications which use this media type:
Pan-European eCall compliant systems
Additional information: None
Magic Number: None
File Extension: None
Macintosh file type code: BINA
Person and email address for further information:
Randall Gellens, rg+ietf@randy.pensive.org
Intended usage: LIMITED USE
Author: The MSD specification was produced by the European
Committee For Standardization (CEN). For contact information,
please see <http://www.cen.eu/cen/Pages/contactus.aspx>.
Change controller: The European Committee For Standardization
(CEN)
14.4. MIME Media Type Registration for application/
EmergencyCallData.Control+xml
IANA has added application/EmergencyCallData.Control+xml as a MIME
media type, with a reference to this document, in accordance to the
procedures of RFC 6838 [RFC6838] and guidelines in RFC 7303
[RFC7303].
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MIME media type name: application
MIME subtype name: EmergencyCallData.Control+xml
Mandatory parameters: none
Optional parameters: charset
Indicates the character encoding of the XML content.
Encoding considerations:
Uses XML, which can employ 8-bit characters, depending on the
character encoding used. See Section 3.2 of RFC 7303
[RFC7303].
Security considerations:
This media type carries metadata and control information and
requests, such as from a Public Safety Answering Point (PSAP)
to an In-Vehicle System (IVS) during an emergency call.
Metadata (such as an acknowledgment that data sent by the IVS
to the PSAP was successfully received) has limited privacy and
security implications. Control information (such as requests
from the PSAP that the vehicle perform an action) has some
privacy and security implications. The privacy concern arises
from the ability to request the vehicle to transmit a data set,
which as described in Section 14.3 can contain personal
information. The security concern is the ability to request
the vehicle to perform an action. Control information needs to
originate only from a PSAP or other emergency services
providers and not be modified en route. The level of integrity
of the cellular network over which the emergency call is placed
is a consideration: when the IVS initiates an eCall over a
cellular network, in most cases it relies on the MNO to route
the call to a PSAP. (Calls placed using other means, such as
Wi-Fi or over-the-top services, generally incur somewhat higher
levels of risk than calls placed "natively" using cellular
networks.) A callback from a PSAP merits additional
consideration, since current mechanisms are not ideal for
verifying that such a call is indeed a callback from a PSAP in
response to an emergency call placed by the IVS. See the
discussion in Section 11 and the PSAP Callback document
[RFC7090].
Sections 7 and 8 of [RFC7852] contain more discussion.
Interoperability considerations: None
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Published specification: This document
Applications which use this media type:
Pan-European eCall compliant systems
Additional information: None
Magic Number: None
File Extension: .xml
Macintosh file type code: TEXT
Person and email address for further information:
Randall Gellens, rg+ietf@randy.pensive.org
Intended usage: LIMITED USE
Author: The IETF ECRIT working group
Change controller: The IETF ECRIT working group
14.5. Registration of the "eCall.MSD" Entry in the Emergency Call Data
Types Registry
IANA has added the "eCall.MSD" entry to the "Emergency Call Data
Types" registry, with a reference to this document; the "Data About"
value is "The Call".
14.6. Registration of the "Control" Entry in the Emergency Call Data
Types Registry
IANA has added the "Control" entry to the "Emergency Call Data Types"
registry, with a reference to this document; the "Data About" value
is "The Call".
14.7. Registration for urn:ietf:params:xml:ns:EmergencyCallData:control
This section registers a new XML namespace, as per the guidelines in
RFC 3688 [RFC3688].
URI: urn:ietf:params:xml:ns:EmergencyCallData:control
Registrant Contact: IETF, ECRIT working group, <ecrit@ietf.org>, as
delegated by the IESG <iesg@ietf.org>.
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XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Namespace for Emergency Call Data Control Block</title>
</head>
<body>
<h1>Namespace for Emergency Call Data Control Block</h1>
<p>See RFC 8147</p>
</body>
</html>
END
14.8. Registry Creation
This document creates a new registry called "Emergency Call Metadata/
Control Data". The following sub-registries are created for this
registry.
14.8.1. Emergency Call Actions Registry
This document creates a new sub-registry called "Emergency Call
Actions". As defined in [RFC5226], this registry operates under
"Expert Review" rules. The expert should determine that the proposed
action is within the purview of a vehicle, is sufficiently
distinguishable from other actions, and is clearly and fully
described. In most cases, a published and stable document is
referenced for the description of the action.
The content of this registry includes:
Name: The identifier to be used in the "action" attribute of a
control <request> element.
Description: A description of the action. In most cases, this will
be a reference to a published and stable document. The
description MUST specify if any attributes or child elements are
optional or mandatory and describe the action to be taken by the
vehicle.
The initial set of values is listed in Table 1.
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+-----------+--------------------------------------+
| Name | Description |
+-----------+--------------------------------------+
| send-data | See Section 9.1.3.1 of this document |
+-----------+--------------------------------------+
Table 1: Emergency Call Actions Registry Initial Values
14.8.2. Emergency Call Action Failure Reasons Registry
This document creates a new sub-registry called "Emergency Call
Action Failure Reasons", which contains values for the "reason"
attribute of the <actionResult> element. As defined in [RFC5226],
this registry operates under "Expert Review" rules. The expert
should determine that the proposed reason is sufficiently
distinguishable from other reasons and that the proposed description
is understandable and correctly worded.
The content of this registry includes:
ID: A short string identifying the reason, for use in the "reason"
attribute of an <actionResult> element.
Description: A description of the reason.
The initial set of values is listed in Table 2.
+------------------+------------------------------------------------+
| ID | Description |
+------------------+------------------------------------------------+
| damaged | Required components are damaged. |
| | |
| data-unsupported | The data item referenced in a "send-data" |
| | request is not supported. |
| | |
| security-failure | The authenticity of the request or the |
| | authority of the requestor could not be |
| | verified. |
| | |
| unable | The action could not be accomplished (a |
| | generic error for use when no other code is |
| | appropriate). |
| | |
| unsupported | The "action" value is not supported. |
+------------------+------------------------------------------------+
Table 2: Emergency Call Action Failure Reasons Registry Initial
Values
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14.9. The EmergencyCallData.eCall.MSD INFO Package
This document registers the EmergencyCallData.eCall.MSD INFO package
in the "Info Packages Registry".
Both endpoints (the IVS and the PSAP equipment) include
EmergencyCallData.eCall.MSD in a Recv-Info header field per [RFC6086]
to indicate the ability to receive INFO requests carrying data as
described here.
Support for the EmergencyCallData.eCall.MSD INFO package indicates
the ability to receive eCall related body parts as specified in this
document.
An INFO request message carrying body parts related to an emergency
call as described in this document has an Info-Package header field
set to "EmergencyCallData.eCall.MSD" per [RFC6086].
The requirements of Section 10 of [RFC6086] are addressed in the
following sections.
14.9.1. Overall Description
This section describes what type of information is carried in INFO
requests associated with the INFO package and for what types of
applications and functionalities User Agents (UAs) can use the INFO
package.
INFO requests associated with the EmergencyCallData.eCall.MSD INFO
package carry data associated with emergency calls as defined in this
document. The application is vehicle-initiated emergency calls
established using SIP. The functionality is to carry vehicle data
and metadata/control information between vehicles and PSAPs.
14.9.2. Applicability
This section describes why the INFO package mechanism, rather than
some other mechanism, has been chosen for the specific use case.
The use of the SIP INFO method is based on an analysis of the
requirements against the intent and effects of the INFO method versus
other approaches (which included the SIP MESSAGE method, the SIP
OPTIONS method, the SIP re-INVITE method, media-plane transport, and
non-SIP protocols). In particular, the transport of emergency call
data blocks occurs within a SIP emergency dialog, per Section 6, and
is normally carried in the initial INVITE request and response; the
use of the SIP INFO method only occurs when emergency-call-related
data needs to be sent mid call. While the SIP MESSAGE method could
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be used, it is not tied to a SIP dialog as is the SIP INFO method and
thus might not be associated with the dialog. Either SIP OPTIONS or
re-INVITE methods could also be used, but they are seen as less clean
than the SIP INFO method. The SIP SUBSCRIBE/NOTIFY method could be
coerced into service, but the semantics are not a good fit, e.g., the
subscribe/notify mechanism provides one-way communication consisting
of (often multiple) notifications from notifier to subscriber
indicating that certain events in notifier have occurred, whereas
what's needed here is two-way communication of data related to the
emergency dialog. Use of media-plane mechanisms was discounted
because the number of messages needing to be exchanged in a dialog is
normally zero or very few, and the size of the data is likewise very
small. The overhead caused by user-plane setup (e.g., to use the
Message Session Relay Protocol (MSRP) as transport) would be
disproportionately large.
Based on the analyses, the SIP INFO method was chosen to provide for
mid-call data transport.
14.9.3. INFO Package Name
The INFO package name is EmergencyCallData.eCall.MSD
14.9.4. INFO Package Parameters
None
14.9.5. SIP Option-Tags
None
14.9.6. INFO Request Body Parts
The body for an EmergencyCallData.eCall.MSD INFO package is a
multipart (normally multipart/mixed) body containing zero or one
application/EmergencyCallData.eCall.MSD parts (containing an MSD) and
zero or more application/EmergencyCallData.Control+xml (containing a
metadata/control object) parts. At least one MSD or metadata/control
body part is expected; the behavior upon receiving an INFO request
with neither is undefined.
The body parts are sent per [RFC6086], and in addition, to align with
how these body parts are sent in SIP messages other than INFO
requests, each associated body part is referenced by a Call-Info
header field at the top level of the SIP message. The body part has
a Content-Disposition header field set to "By-Reference".
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An MSD or metadata/control block is always enclosed in a multipart
body part (even if it would otherwise be the only body part in the
SIP message). The outermost multipart that contains only body parts
associated with the INFO package has a Content-Disposition value of
"Info-Package".
14.9.7. INFO Package Usage Restrictions
Usage is limited to vehicle-initiated emergency calls as defined in
this document.
14.9.8. Rate of INFO Requests
The SIP INFO request is used within an established emergency call
dialog for the PSAP to request the IVS to send an updated MSD and for
the IVS to send a requested MSD. Because this is normally done only
on manual request of the PSAP call taker (who suspects some aspect of
the vehicle state has changed), the rate of SIP INFO requests
associated with the EmergencyCallData.eCall.MSD INFO package is
normally quite low (most dialogs are likely to contain zero INFO
requests, while others might carry an occasional request).
14.9.9. INFO Package Security Considerations
The MIME media type registrations specified for use with this INFO
package (Sections 14.3 and 14.4) contain a discussion of the security
and/or privacy considerations specific to that data block. See
Sections 11 and 12 for a discussion of the security and privacy
considerations of the data carried in eCalls.
14.9.10. Implementation Details
See Sections 6 and 7 for protocol details.
14.9.11. Examples
See Section 10 for protocol examples.
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15. References
15.1. Normative References
[MSD] European Committee for Standardization, "Intelligent
transport systems - eSafety - eCall minimum set of data
(MSD)", Standard: CEN - EN 15722, April 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<http://www.rfc-editor.org/info/rfc3688>.
[RFC5031] Schulzrinne, H., "A Uniform Resource Name (URN) for
Emergency and Other Well-Known Services", RFC 5031,
DOI 10.17487/RFC5031, January 2008,
<http://www.rfc-editor.org/info/rfc5031>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC6086] Holmberg, C., Burger, E., and H. Kaplan, "Session
Initiation Protocol (SIP) INFO Method and Package
Framework", RFC 6086, DOI 10.17487/RFC6086, January 2011,
<http://www.rfc-editor.org/info/rfc6086>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
[RFC6881] Rosen, B. and J. Polk, "Best Current Practice for
Communications Services in Support of Emergency Calling",
BCP 181, RFC 6881, DOI 10.17487/RFC6881, March 2013,
<http://www.rfc-editor.org/info/rfc6881>.
[RFC7303] Thompson, H. and C. Lilley, "XML Media Types", RFC 7303,
DOI 10.17487/RFC7303, July 2014,
<http://www.rfc-editor.org/info/rfc7303>.
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RFC 8147 Next-Generation eCall May 2017
[RFC7852] Gellens, R., Rosen, B., Tschofenig, H., Marshall, R., and
J. Winterbottom, "Additional Data Related to an Emergency
Call", RFC 7852, DOI 10.17487/RFC7852, July 2016,
<http://www.rfc-editor.org/info/rfc7852>.
15.2. Informative references
[CEN] "European Committee for Standardization (CEN)",
<http://www.cen.eu>.
[EN_16062] European Committee for Standardization, "Intelligent
transport systems - eSafety - eCall High Level Application
Requirements (HLAP) Using GSM/UMTS Circuit Switched
Networks", Standard: CEN - EN 16062, April 2015.
[EN_16072] European Committee for Standardization, "Intelligent
transport systems - eSafety - Pan-European eCall operating
requirements", Standard: CEN - EN 16072, April 2015.
[MSG_TR] ETSI, "Mobile Standards Group (MSG); eCall for VoIP",
ETSI TR 103 140 V1.1.1, April 2014.
[RFC5012] Schulzrinne, H. and R. Marshall, Ed., "Requirements for
Emergency Context Resolution with Internet Technologies",
RFC 5012, DOI 10.17487/RFC5012, January 2008,
<http://www.rfc-editor.org/info/rfc5012>.
[RFC5069] Taylor, T., Ed., Tschofenig, H., Schulzrinne, H., and M.
Shanmugam, "Security Threats and Requirements for
Emergency Call Marking and Mapping", RFC 5069,
DOI 10.17487/RFC5069, January 2008,
<http://www.rfc-editor.org/info/rfc5069>.
[RFC6443] Rosen, B., Schulzrinne, H., Polk, J., and A. Newton,
"Framework for Emergency Calling Using Internet
Multimedia", RFC 6443, DOI 10.17487/RFC6443, December
2011, <http://www.rfc-editor.org/info/rfc6443>.
[RFC7090] Schulzrinne, H., Tschofenig, H., Holmberg, C., and M.
Patel, "Public Safety Answering Point (PSAP) Callback",
RFC 7090, DOI 10.17487/RFC7090, April 2014,
<http://www.rfc-editor.org/info/rfc7090>.
[RFC7378] Tschofenig, H., Schulzrinne, H., and B. Aboba, Ed.,
"Trustworthy Location", RFC 7378, DOI 10.17487/RFC7378,
December 2014, <http://www.rfc-editor.org/info/rfc7378>.
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[RFC8148] Gellens, R., Rosen, B., and H. Tschofenig, "Next-
Generation Vehicle-Initiated Emergency Calls", RFC 8148,
DOI 10.17487/RFC8148, May 2017,
<http://www.rfc-editor.org/info/rfc8148>.
[SDO-3GPP] "3rd Generation Partnership Project (3GPP)",
<http://www.3gpp.org/>.
[SDO-ETSI] "European Telecommunications Standards Institute (ETSI)",
<http://www.etsi.org>.
[TS22.101] 3GPP, "Universal Mobile Telecommunications System (UMTS);
Service aspects; Service principles", 3GPP TS
22.101, version 8.7.0, Release 8, January 2008.
[TS23.167] 3GPP, "IP Multimedia Subsystem (IMS) emergency sessions",
3GPP TS 23.167, version 9.6.0, Release 9, March 2011.
[TS24.229] 3GPP, "IP multimedia call control protocol based on
Session Initiation Protocol (SIP) and Session Description
Protocol (SDP); Stage 3", 3GPP TS 24.229, version 12.6.0,
Release 12, October 2014.
Acknowledgments
We would like to thank Bob Williams and Ban Al-Bakri for their
feedback and suggestions; Rex Buddenberg, Lena Chaponniere, Alissa
Cooper, Keith Drage, Stephen Edge, Wes George, Mirja Kuehlewind,
Allison Mankin, Alexey Melnikov, Ivo Sedlacek, and James Winterbottom
for their review and comments; Robert Sparks and Paul Kyzivat for
their help with the SIP mechanisms; and Mark Baker and Ned Freed for
their help with the media subtype registration issue. We would like
to thank Michael Montag, Arnoud van Wijk, Gunnar Hellstrom, and
Ulrich Dietz for their help with the original document upon which
this document is based. Christer Holmberg deserves special mention
for his many detailed reviews.
Contributors
Brian Rosen was a co-author of the original document upon which this
document is based.
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Authors' Addresses
Randall Gellens
Core Technology Consulting
Email: rg+ietf@coretechnologyconsulting.com
URI: http://www.coretechnologyconsulting.com
Hannes Tschofenig
Individual
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
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