RFC 8147
Next-Generation Pan-European eCall
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 eCallAbstract
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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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
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.
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
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 Point3. 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]).
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.
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).
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
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
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
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
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.
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"/>
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.
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 IVS9.1.2. 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".
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 Example9.1.3. 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"
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.
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
(next page on part 2)
