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rfc:rfc8147

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.

Gellens & Tschofenig Standards Track [Page 1] RFC 8147 Next-Generation eCall May 2017

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] RFC 8147 Next-Generation eCall May 2017

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

Gellens & Tschofenig Standards Track [Page 3] RFC 8147 Next-Generation eCall May 2017

     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.

Gellens & Tschofenig Standards Track [Page 4] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 5] RFC 8147 Next-Generation eCall May 2017

 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]).

Gellens & Tschofenig Standards Track [Page 6] RFC 8147 Next-Generation eCall May 2017

 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.

Gellens & Tschofenig Standards Track [Page 7] RFC 8147 Next-Generation eCall May 2017

 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).

Gellens & Tschofenig Standards Track [Page 8] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 9] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 10] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 11] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 12] RFC 8147 Next-Generation eCall May 2017

 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.

Gellens & Tschofenig Standards Track [Page 13] RFC 8147 Next-Generation eCall May 2017

 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"/>

Gellens & Tschofenig Standards Track [Page 14] RFC 8147 Next-Generation eCall May 2017

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.

Gellens & Tschofenig Standards Track [Page 15] RFC 8147 Next-Generation eCall May 2017

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".

Gellens & Tschofenig Standards Track [Page 16] RFC 8147 Next-Generation eCall May 2017

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"

Gellens & Tschofenig Standards Track [Page 17] RFC 8147 Next-Generation eCall May 2017

 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.

Gellens & Tschofenig Standards Track [Page 18] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 19] RFC 8147 Next-Generation eCall May 2017

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

Gellens & Tschofenig Standards Track [Page 20] RFC 8147 Next-Generation eCall May 2017

 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

Gellens & Tschofenig Standards Track [Page 21] RFC 8147 Next-Generation eCall May 2017

 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: ...
  1. -boundary1

Content-Type: application/sdp

         ...Session Description Protocol (SDP) goes here...
  1. -boundary1

Content-Type: application/pidf+xml

    Content-ID: <target123@example.com>
    Content-Disposition: by-reference;handling=optional
          ...PIDF-LO goes here...
  1. -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...
  1. -boundary1–
                     Figure 8: SIP NG-eCall INVITE

Gellens & Tschofenig Standards Track [Page 22] RFC 8147 Next-Generation eCall May 2017

 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: ...
  1. -boundaryX

Content-Type: application/sdp

         ...Session Description Protocol (SDP) goes here...
  1. -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>
  1. -boundaryX–
                  Figure 9: 200 OK Response to INVITE

Gellens & Tschofenig Standards Track [Page 23] RFC 8147 Next-Generation eCall May 2017

 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: ...
  1. -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

Gellens & Tschofenig Standards Track [Page 24] RFC 8147 Next-Generation eCall May 2017

 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: ...
  1. -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...
  1. -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.

Gellens & Tschofenig Standards Track [Page 25] RFC 8147 Next-Generation eCall May 2017

 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.)

Gellens & Tschofenig Standards Track [Page 26] RFC 8147 Next-Generation eCall May 2017

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"/>

Gellens & Tschofenig Standards Track [Page 27] RFC 8147 Next-Generation eCall May 2017

                  <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"/>

Gellens & Tschofenig Standards Track [Page 28] RFC 8147 Next-Generation eCall May 2017

                  <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"/>

Gellens & Tschofenig Standards Track [Page 29] RFC 8147 Next-Generation eCall May 2017

                  <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

Gellens & Tschofenig Standards Track [Page 30] RFC 8147 Next-Generation eCall May 2017

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

Gellens & Tschofenig Standards Track [Page 31] RFC 8147 Next-Generation eCall May 2017

    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].

Gellens & Tschofenig Standards Track [Page 32] RFC 8147 Next-Generation eCall May 2017

    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

Gellens & Tschofenig Standards Track [Page 33] RFC 8147 Next-Generation eCall May 2017

    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>.

Gellens & Tschofenig Standards Track [Page 34] RFC 8147 Next-Generation eCall May 2017

 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.

Gellens & Tschofenig Standards Track [Page 35] RFC 8147 Next-Generation eCall May 2017

         +-----------+--------------------------------------+
         |    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

Gellens & Tschofenig Standards Track [Page 36] RFC 8147 Next-Generation eCall May 2017

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

Gellens & Tschofenig Standards Track [Page 37] RFC 8147 Next-Generation eCall May 2017

 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".

Gellens & Tschofenig Standards Track [Page 38] RFC 8147 Next-Generation eCall May 2017

 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.

Gellens & Tschofenig Standards Track [Page 39] RFC 8147 Next-Generation eCall May 2017

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>.

Gellens & Tschofenig Standards Track [Page 40] 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>.

Gellens & Tschofenig Standards Track [Page 41] RFC 8147 Next-Generation eCall May 2017

 [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.

Gellens & Tschofenig Standards Track [Page 42] RFC 8147 Next-Generation eCall May 2017

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

Gellens & Tschofenig Standards Track [Page 43]

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