RFC 8148
Next-Generation Vehicle-Initiated Emergency Calls
Internet Engineering Task Force (IETF) R. Gellens Request for Comments: 8148 Core Technology Consulting Category: Standards Track B. Rosen ISSN: 2070-1721 NeuStar, Inc. H. Tschofenig Individual May 2017 Next-Generation Vehicle-Initiated Emergency CallsAbstract
This document describes how to use IP-based emergency services mechanisms to support the next generation of emergency calls placed by vehicles (automatically in the event of a crash or serious incident, or manually invoked by a vehicle occupant) and conveying vehicle, sensor, and location data related to the crash or incident. Such calls are often referred to as "Automatic Crash Notification" (ACN), or "Advanced Automatic Crash Notification" (AACN), even in the case of manual trigger. The "Advanced" qualifier refers to the ability to carry a richer set of data. This document also registers a MIME media type and Emergency Call Data Type for the vehicle, sensor, and location data (often referred to as "crash data" even though there is not necessarily a crash) and an INFO package to enable carrying this and related data in SIP INFO requests. An external specification for the data format, contents, and structure is referenced in this document. This document reuses the technical aspects of next-generation Pan- European eCall (a mandated and standardized system for emergency calls by in-vehicle systems (IVSs) within Europe and other regions). However, this document specifies use of a different set of vehicle (crash) data, specifically, the Vehicle Emergency Data Set (VEDS) rather than the eCall Minimum Set of Data (MSD). This document is an extension of the IETF eCall document, with the primary differences being that this document makes the MSD data set optional and VEDS mandatory, and it adds attribute values to the metadata/control object to permit greater functionality. This document registers a new INFO package (identical to that registered for eCall but with the addition of the VEDS MIME type). This document also describes legacy (circuit-switched) ACN systems and their migration to next-generation emergency calling, to provide background information and context.
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/rfc8148. 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Document Scope . . . . . . . . . . . . . . . . . . . . . . . 8 4. Overview of Legacy Deployment Models . . . . . . . . . . . . 8 5. Migration to Next Generation . . . . . . . . . . . . . . . . 10 6. Vehicle Data . . . . . . . . . . . . . . . . . . . . . . . . 13 7. Data Transport . . . . . . . . . . . . . . . . . . . . . . . 14 8. Call Setup . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. New Metadata/Control Values . . . . . . . . . . . . . . . . . 17 9.1. New Values for the "action" Attribute . . . . . . . . . . 18 9.2. Example <request> Element . . . . . . . . . . . . . . . . 19 9.3. The <ack> Element . . . . . . . . . . . . . . . . . . . . 19 9.4. The <capabilities> Element . . . . . . . . . . . . . . . 20 10. Test Calls . . . . . . . . . . . . . . . . . . . . . . . . . 21 11. Example Call Initiation . . . . . . . . . . . . . . . . . . . 22 12. Security Considerations . . . . . . . . . . . . . . . . . . . 27 13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 28 14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28 14.1. MIME Media Type Registration for application/EmergencyCall.VEDS+xml . . . . . . . . . . . 28 14.2. Registration of the "VEDS" Entry in the Emergency Call Data Types Registry . . . . . . . . . . . . . . . . . . 30 14.3. New Action Values . . . . . . . . . . . . . . . . . . . 30 14.4. Emergency Call Static Messages Registry . . . . . . . . 31 14.5. Emergency Call Vehicle Lamp IDs Registry . . . . . . . . 32 14.6. Emergency Call Vehicle Camera IDs Registry . . . . . . . 33 14.7. The EmergencyCallData.VEDS INFO Package . . . . . . . . 35 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 15.1. Normative References . . . . . . . . . . . . . . . . . . 38 15.2. Informative references . . . . . . . . . . . . . . . . . 39 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 40 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40
1. Introduction
Emergency calls made by in-vehicle systems (e.g., automatically in the event of a crash or serious incident or manually by a vehicle occupant) assist in significantly reducing road deaths and injuries by allowing emergency services to respond quickly and appropriately to the specifics of the incident, often with better location accuracy. Drivers often have a poor location awareness, especially outside of major cities, at night, and when away from home (especially abroad). In the most crucial cases, the victim(s) might not be able to call because they have been injured or trapped. For more than two decades, some vehicles have been equipped with telematics systems that, among other features, place an emergency call automatically in the event of a crash or manually in response to an emergency call button. Such systems generally have on-board location determination systems that make use of satellite-based positioning technology, inertial sensors, gyroscopes, etc., which can provide an accurate position for the vehicle. Such built-in systems can take advantage of the benefits of being integrated into a vehicle, such as more power capacity, ability to have larger or specialized antenna, ability to be engineered to avoid or minimize degradation by vehicle glass coatings, interference from other vehicle systems, etc. Thus, the Public Safety Answering Point (PSAP) can be provided with a good estimate of where the vehicle is during an emergency. Vehicle manufacturers are increasingly adopting such systems, both for the safety benefits and for the additional features and services they enable (e.g., remote engine diagnostics, remote door unlock, stolen vehicle tracking and disabling, etc.). A common term for such systems is Automatic Crash Notification (ACN) or Advanced Automatic Crash Notification (AACN). Sometimes the word "Collision" is used instead of "Crash." In this document, "ACN" is used as a general term. ACN systems transmit some amount of data specific to the incident, referred to generally as "crash data" (the term is commonly used even though there might not have been a crash). While different systems transmit different amounts of crash data, standardized formats, structures, and mechanisms are needed to provide interoperability among systems and PSAPs. As of the date of this document, currently deployed in-vehicle telematics systems are circuit-switched and lack a standards-based ability to convey crash data directly to the PSAP (generally relying on either a human advisor or an automated text-to-speech system to provide the PSAP call taker with some crash data orally, or in some cases via a proprietary mechanism). In most cases, the PSAP call
taker needs to first realize that the call is related to a vehicle incident, and then listen to the data and transcribe it. Circuit- switched ACN systems are referred to here as "CS-ACN". The transition to next-generation emergency calling provides an opportunity to vastly improve the scope, breadth, reliability, and usefulness of crash data by transmitting a standardized set during call setup; the data can be processed by the PSAP in an integrated, automated way and made available to the call taker at call presentation. It also provides the ability for the call taker to request that a vehicle take certain actions, such as flashing lights or unlocking doors. In addition, vehicle manufacturers are provided an opportunity to take advantage of the same standardized mechanisms for data transmission and request processing for internal use if they wish (such as telemetry between the vehicle and a service center for both emergency and non-emergency uses, including location-based services, multimedia entertainment systems, remote door unlocking, remote diagnostics, and roadside assistance applications). Next-generation ACN provides an opportunity for such calls to be recognized and processed as such during call setup, and routed to an equipped PSAP where the vehicle data is available to assist the call taker in assessing and responding to the situation. Next-generation (IP-based) ACN systems are referred to here as NG-ACN. An ACN call can be initiated by a vehicle occupant or automatically initiated by vehicle systems in the event of a serious incident. (The "A" in "ACN" does stand for "Automatic", but the term is broadly used to refer to the class of calls that are placed by an in-vehicle system (IVS) or by Telematics Service Providers (TSPs) and that carry incident-related data as well as voice.) Automatically triggered calls indicate a car crash or some other serious incident (e.g., a fire). Manually triggered calls include reports of observed crashes or serious hazards (such as impaired drivers or roadway debris), requests for medical assistance, etc. The Association of Public-Safety Communications Officials (APCO) and the National Emergency Number Association (NENA) have jointly developed a standardized set of incident-related vehicle data for ACN use, called the Vehicle Emergency Data Set (VEDS) [VEDS]. Such data is often referred to as crash data although it is applicable in incidents other than crashes. This document describes how the IETF mechanisms for IP-based emergency calls are used to provide the realization of next- generation ACN. Although this specification is designed with the requirements for North America ACN in mind (and both APCO and NENA are based in the U.S.), it is specified generically such that the
technology can be reused or extended to suit requirements in other regions. This document reuses the technical aspects of next-generation Pan- European eCall (a mandated and standardized system for emergency calls by in-vehicle systems within Europe), as described in [RFC8147]. However, this document specifies use of a different set of vehicle (crash) data, specifically, VEDS rather than the eCall Minimum Set of Data (MSD). This document is an extension of [RFC8147], with the differences being that this document makes the MSD data set optional and VEDS mandatory, and it adds new attribute values to the metadata/control object defined in that document. This document also registers a new INFO package (identical to that defined in [RFC8147] with the addition of the VEDS MIME type). This document registers the application/EmergencyCallData.VEDS+xml MIME media type, the VEDS Emergency Call Data Type, and the EmergencyCallData.VEDS INFO package to enable carrying this and related data in SIP INFO requests. Section 6 introduces VEDS. Section 7 describes how VEDS data and metadata/control blocks are transported within NG-ACN calls. Section 8 describes how such calls are placed. These mechanisms are used to place emergency calls that are identifiable as ACN calls and that carry standardized crash data in an interoperable way. Calls by in-vehicle systems are placed using cellular networks, which might ignore location information sent by an originating device in an emergency call INVITE, instead substituting their own location information (although often determined in cooperation with the originating device). Standardized crash data structures typically include location as determined by the IVS. A benefit of this is that it allows the PSAP to see both the location as determined by the cellular network and the location as determined by the IVS. This specification inherits the ability to utilize test call functionality from Section 15 of [RFC6881].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 AACN: Advanced Automatic Crash Notification ACN: Automatic Crash Notification APCO: Association of Public-Safety Communications Officials EENA: European Emergency Number Association ESInet: Emergency Services IP network GNSS: Global Navigation Satellite System (which includes various systems such as the Global Positioning System or GPS) IVS: In-Vehicle System MNO: Mobile Network Operator MSD: Minimum Set of Data NENA: National Emergency Number Association NG: Next Generation POTS: Plain Old Telephone Service (normal, circuit-switched voice calls) PSAP: Public Safety Answering Point TSP: Telematics Service Provider VEDS: Vehicle Emergency Data Set Because the endpoints of a next-generation ACN call are a PSAP and either an IVS or a TSP, to avoid repetitively writing "IVS or TSP", the term "IVS" is used to represent either an IVS or a TSP when discussing signaling behavior (e.g., sending VEDS data, sending a SIP INVITE request, receiving a SIP INFO request, etc.).
3. Document Scope
This document is focused on how an ACN emergency call is set up and incident-related data (including vehicle, sensor, and location data) is transmitted to the PSAP using IETF specifications. For the direct model, this is the end-to-end description (between the vehicle and the PSAP). For the TSP model, this describes the call leg between the TSP and the PSAP, leaving the call leg between the vehicle and the TSP up to the entities involved (i.e., IVS and TSP vendors) who are free to use the same mechanism for both legs, or not. Note that Europe has a mandated and standardized system for emergency calls by in-vehicle systems. This Pan-European system is known as "eCall" and is the subject of a separate document, [RFC8147], which this document builds on. Vehicles designed to operate in multiple regions might need to support eCall as well as NG-ACN as described here. A vehicle IVS might determine whether to use eCall or ACN by first determining the region or country in which it is located (e.g., from a GNSS location estimate and/or identity of or information from an MNO). If other regions adopt other data formats, a multi-region vehicle might need to support those as well. This document adopts the call setup and other technical aspects of [RFC8147], which uses [RFC7852]; this makes it straightforward to use a different data set while keeping other technical aspects unchanged. Hence, both next- generation eCall (NG-eCall) and the NG-ACN mechanism described here are compatible, differing primarily in the specific data block that is sent (the eCall MSD in the case of NG-eCall and VEDS in this document) and some additions to the metadata/control data block. If other regions adopt their own vehicle data sets, this can be similarly accommodated without changing other technical aspects. Note that any additional data formats require a new INFO package to permit transport within SIP INFO requests.4. Overview of Legacy Deployment Models
Legacy (circuit-switched) systems for placing emergency calls by in-vehicle systems generally have some ability to convey at least location and in some cases telematics data to the PSAP. Most such systems use one of three architectural models, which are described here as: "TSP", "direct", and "paired". These three models are illustrated below. In the TSP model, both emergency and routine TSP service calls are placed to a TSP; a proprietary technique (e.g., a proprietary in-band modem) is used for data transfer between the TSP and the vehicle.
In an emergency, typically a TSP agent verifies the emergency, bridges in the PSAP, and communicates location, crash data (such as impact severity and trauma prediction), and other data (such as the vehicle description) to the PSAP call taker orally (in some cases, a proprietary out-of-band interface is used). Since the TSP knows the location of the vehicle (from on-board GNSS and sensors), location- based routing is usually used to route to the appropriate PSAP. In some cases, the TSP is able to transmit location automatically, using similar techniques as for wireless calls. A three-way voice call is generally established between the vehicle, the TSP, and the PSAP, allowing communication between the PSAP call taker, the TSP agent, and the vehicle occupants (who might be unconscious). ///----\\\ proprietary +-----+ 911 trunk or POTS +------+ ||| IVS |||-------------->| TSP |--------------------->| PSAP | \\\----/// crash data +-----+ location via trunk +------+ Figure 1: Legacy TSP Model In the paired model, the IVS uses a local link (typically Bluetooth [Bluetooth]) with a previously paired handset to establish an emergency call with the PSAP (by dialing a standard emergency number; 9-1-1 in North America) and then communicates location data to the PSAP via text-to-speech; crash data might or might not be conveyed also using text-to-speech. Some such systems use an automated voice prompt menu for the PSAP call taker (e.g., "this is an automatic emergency call from a vehicle; press 1 to open a voice path to the vehicle; press 2 to hear the location read out") to allow the call taker to request location data via text-to-speech. ///----\\\ +----+ 911/etc. voice call via handset +------+ ||| IVS |||-->| HS |----------------------------------->| PSAP | \\\----/// +----+ location via text-to-speech +------+ (Note: "HS" is handset.) Figure 2: Legacy Paired Model In the direct model, the IVS directly places an emergency call with the PSAP by dialing a standard emergency number (9-1-1 in North America). Such systems might communicate location data to the PSAP via text-to-speech; crash data might or might not be conveyed using text-to-speech. Some such systems use an automated voice prompt menu (e.g., "this is an automatic emergency call from a vehicle; press 1 to open a voice path to the vehicle; press 2 to hear the location read out") to allow the call taker to request location data via text-to-speech.
///----\\\ 911/etc. voice call via IVS +------+ ||| IVS |||---------------------------------------->| PSAP | \\\----/// location via text-to-speech +------+ Figure 3: Legacy Direct Model5. Migration to Next Generation
The migration of emergency calls placed by in-vehicle systems to next-generation (all-IP) technology per this document provides a standardized mechanism to identify such calls and to convey crash data with the call setup, as well as enabling additional communications modalities and enhanced functionality. This allows ACN calls and crash data to be automatically processed by the PSAP and made available to the call taker in an integrated, automated way. Because the crash data is carried in the initial SIP INVITE (per [RFC7852]) the PSAP can present it to the call taker simultaneously with the appearance of the call. The PSAP can also process the data to take other actions (e.g., if multiple calls from the same location arrive when the PSAP is busy and a subset of them are NG-ACN calls, a PSAP might choose to store the information and reject the calls, since the IVS will receive confirmation that the information has been successfully received; a PSAP could also choose to include a message stating that it is aware of the incident and responders are on the way, and a PSAP could call the vehicle back when a call taker is available). The migration of origination devices and networks, PSAPs, emergency services networks, and other telephony environments to next generation technology provides enhanced interoperability and functionality, especially for emergency calls carrying additional data such as vehicle crash data. (In the U.S., a network specifically for emergency responders is being developed. This network, FirstNet, will be next generation from the start, enhancing the ability for data exchange between PSAPs and responders.) NG-ACN calls can be recognized as such during call set-up; they can be routed to a PSAP that is prepared both technically and operationally to handle such calls, and the vehicle-determined location and crash data can be processed automatically by the PSAP and made available to the call taker simultaneously with the call appearance. Enhanced functionality includes the ability for the PSAP call taker to request the vehicle to take an action, such as sending an updated set of data, conveying a message to the occupants, flashing lights, unlocking doors, etc.
Vehicle manufacturers using the TSP model can choose to take advantage of the same mechanism to carry telematics data and requests and responses between the vehicle and the TSP for both emergency and non-emergency calls as are used for the interface with the PSAP. An IVS establishes a next-generation emergency call (see [RFC6443] and [RFC6881]) with an initial INVITE containing a Request-URI indicating an ACN emergency call and Call-Info header fields indicating that both vehicle crash and capabilities data are included; the IVS typically does not perform routing or location queries (relying on the MNO for this). [RFC8147] registers new service URN children within the "sos" subservice. These URNs request NG-ACN resources and differentiate between manually and automatically triggered NG-ACN calls (which might be subject to different treatment depending on policy). The two service URNs registered in [RFC8147] are "urn:service:sos.ecall.automatic" and "urn:service:sos.ecall.manual". The same service URNs are used for ACN as for eCall since in any region only one of these is supported, making a distinction unnecessary. (Further, PSAP equipment might support multiple data formats, allowing a PSAP to handle a vehicle that erroneously sent the wrong data object.) Note that in North America, routing queries performed by clients outside of an ESInet typically treat all sub-services of "sos" identically to "sos" with no sub-service. However, the Request-URI header field retains the full sub-service; route and handling decisions within an ESInet or PSAP can take the sub-service into account. For example, in a region with multiple cooperating PSAPs, an NG-ACN call might be routed to a PSAP that is NG-ACN capable, or one that specializes in vehicle-related incidents. Migration of the three architectural models to next generation (all-IP) is described below. In the TSP model, the IVS transmits crash and location data to the TSP either by reusing the mechanisms and data objects described in this document or by using a proprietary mechanism. In an emergency, the TSP bridges in the PSAP, and the TSP transmits crash and other data to the PSAP using the mechanisms and data objects described in this document. There is a three-way call between the vehicle, the TSP, and the PSAP, allowing communication between the PSAP call taker, the TSP agent, and the vehicle occupants (who might be unconscious). The TSP relays PSAP requests and vehicle responses.
proprietary ///----\\\ or standard +-----+ standard +------+ ||| IVS |||------------------->| TSP |------------------->| PSAP | \\\----/// crash+other data +-----+ crash+other data +------+ Figure 4: Next-Generation TSP Model The vehicle manufacturer and the TSP can choose to use the same mechanisms and data objects on the left call leg in Figure 4 as on the right. (Note that the TSP model can be more difficult when the vehicle is in a different country than the TSP (e.g., a US resident driving in Canada) because of the additional complexity in choosing the correct PSAP based on vehicle location performed by a TSP in a different country.) In the direct model, the IVS communicates crash data to the PSAP directly using the mechanisms and data objects described in this document. ///----\\\ NG emergency call +------+ ||| IVS |||----------------------------------------->| PSAP | \\\----/// crash + other data +------+ Figure 5: Next-Generation Direct Model In the paired model, the IVS uses a local link to a previously paired handset to establish an emergency call with the PSAP; it is unclear what facilities are or will be available for transmitting crash data through the link to the handset for inclusion in an NG emergency call and receiving additional data items from the response. Hence, manufacturers that use the paired model for legacy calls might choose to adopt either the direct or TSP model for next-generation calls. ///----\\\ (undefined) +----+ standard +------+ ||| IVS |||----------------->| HS |--------------------->| PSAP | \\\----/// (undefined) +----+ crash + other data +------+ Figure 6: Next-Generation Paired Model Regardless of model, if the call is routed to a PSAP that is not NG-ACN capable, the PSAP ignores (or does not receive) the vehicle data. This is detectable by the IVS or TSP when the status response to the INVITE (e.g., 200 OK) lacks a metadata/control structure acknowledging receipt of the data [RFC8147]. The IVS or TSP then proceeds as it would for a CS-ACN call (e.g., oral conveyance of data).
6. Vehicle Data
APCO and NENA have jointly developed a standardized set of incident- related vehicle data for ACN use, called the Vehicle Emergency Data Set (VEDS) [VEDS]. Such data is often referred to as crash data although it is applicable in incidents other than crashes. VEDS provides a standard data set for the transmission, exchange, and interpretation of vehicle-related data. A standard data format allows the data to be generated by an IVS or TSP and interpreted by PSAPs, emergency responders, and medical facilities. It includes incident-related information such as airbag deployment, location and compass orientation of the vehicle, spatial orientation of the vehicle (e.g., upright, on a side, roof, or bumper), sensor data that can indicate the potential severity of the crash and the likelihood of severe injuries to the vehicle occupants, etc. This data better informs the PSAP and emergency responders as to the type of response that might be needed. Some of this information has been included in U.S. government guidelines for field triage of injured patients [triage-2008] [triage-2011]. These guidelines are designed to help responders identify the potential existence of severe internal injuries and to make critical decisions about how and where a patient needs to be transported. VEDS is an XML structure (see [VEDS]) transported in SIP using the application/EmergencyCallData.VEDS+xml MIME media type. If new data blocks are needed (e.g., in other regions or for enhanced data), the steps required during standardization are briefly summarized below: o A set of data is standardized by a Standards Development Organization (SDO) or appropriate organization. o A MIME media type for the crash data set is registered with IANA * If the data is specifically for use in emergency calling, the MIME media type is normally under the application type with a subtype starting with EmergencyCallData. * If the data format is XML, then by convention the name has a suffix of "+xml".
o The item is registered in the "Emergency Call Data Types"
registry, as defined in Section 11.1.9 of [RFC7852].
* For emergency-call-specific formats, the registered name is the
root of the MIME media type (not including the
EmergencyCallData prefix and any suffix such as "+xml") as
described in Section 4.1 of [RFC7852].
o A new INFO package is registered that permits carrying the new
media type, the metadata/control object (defined in [RFC8147]),
and for compatibility, the MSD and VEDS objects, in SIP INFO
requests.
7. Data Transport
[RFC7852] establishes a general mechanism for including blocks of
data within a SIP emergency call. This document makes use of that
mechanism. This document also registers an INFO package (in
Section 14.7) to enable NG-ACN-related data blocks to be carried in
SIP INFO requests (per [RFC6086], new SIP INFO method usages require
the definition of an INFO package).
VEDS is an XML structure defined by APCO and NENA [VEDS]. It is
carried in a body part with MIME media type application/
EmergencyCallData.VEDS+xml.
An IVS transmits a VEDS data block (see [VEDS]) by including it as a
body part of a SIP message per [RFC7852]. The body part is
identified by its MIME media type (application/
EmergencyCallData.VEDS+xml) 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 VEDS data 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 a VEDS data block per the
"Emergency Call Data Types" registry entry; the "purpose" parameter's
value is "EmergencyCallData.VEDS". A VEDS data block is carried in a
SIP INFO request by using the INFO package defined in Section 14.7.
A PSAP or IVS transmits a metadata/control object (see [RFC8147]) by
including it in 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 that is
listed in a Content-ID header field in the body part. The SIP
message is marked as containing the metadata/control block 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 a metadata/control block per the "Emergency Call Data Types" registry entry; the "purpose" parameter's value is "EmergencyCallData.Control". A metadata/control object is carried in a SIP INFO request by using the INFO package defined in Section 14.7. A body part containing a VEDS or metadata/control object has a Content-Disposition header field value containing "By-Reference" and is always enclosed in a multipart body part (even if it would otherwise be the only body part in the SIP message). An IVS initiating an NG-ACN call includes in the initial INVITE a VEDS data block and a metadata/control object informing the PSAP of its capabilities. The VEDS and metadata/control body parts (and Presence Information Data Format Location Object (PIDF-LO)) have a Content-Disposition header field with the value "By-Reference; handling=optional". Specifying handling=optional prevents the INVITE 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 VEDS or metadata/control (or PIDF-LO) objects. The PSAP creates a metadata/control object acknowledging receipt of the VEDS data and includes it in the SIP final response to the INVITE. The metadata/control object is not included in provisional (e.g., 180) responses. If the IVS receives an acknowledgment for a VEDS data object with received=false, this indicates that the PSAP was unable to properly decode or process the VEDS. The IVS action is not defined (e.g., it might only log an error). Since the PSAP is able to request an updated VEDS during the call, if an initial VEDS is unsatisfactory in any way, the PSAP can choose to request another one. A PSAP can request that the vehicle send an updated VEDS data block during a call. To do so, the PSAP creates a metadata/control object requesting VEDS data and includes it as a body part of a SIP INFO request sent within the dialog. The IVS then includes an updated VEDS data object as a body part of a SIP INFO request and sends it within the dialog. If the IVS is unable to send the VEDS for any reason, it instead sends a metadata/control object containing an <ack> element acknowledging the request and containing an <actionResult> element with the "success" parameter set to "false" and a "reason" parameter (and optionally a "details" parameter) indicating why the request cannot be accomplished. Per [RFC6086], metadata/control objects and VEDS data are sent using the INFO package defined in Section 14.7. In addition, to align with the way
a VEDS or metadata/control block is transmitted in a SIP message other than a SIP INFO request, one or more Call-Info header fields are included in the SIP INFO request referencing the VEDS or metadata/control block. See Section 14.7 for more information on the use of SIP INFO requests within NG-ACN calls. Any metadata/control object sent by a PSAP can request that the vehicle perform an action (such as sending a data block, flashing lights, providing a camera feed, etc.). The IVS sends an acknowledgment for any request other than a successfully executed send-data action. Multiple requests with the same "action:" value MUST be sent in separate metadata/control body parts (to avoid any ambiguity in the acknowledgment). For each metadata/control block received containing one or more <request> elements (except for successfully executed send-data requests), the IVS sends a metadata/ control object containing an <ack> element acknowledging the received metadata/control block, containing an <actionResult> element per <request> element. If the IVS is aware that VEDS data it sent previously has changed, it MAY send an unsolicited VEDS in any convenient SIP message, including a SIP INFO request during the call. The PSAP sends an acknowledgment for an unsolicited VEDS object; if the IVS sent the unsolicited VEDS in a SIP INFO request, the acknowledgment is sent in a new SIP INFO request; otherwise, it is sent in the reply to the SIP request containing the VEDS.8. Call Setup
An IVS initiating an NG-ACN call sends a SIP INVITE request using one of the SOS sub-services "SOS.ecall.automatic" or "SOS.ecall.manual" in the Request-URI. This SIP INVITE request includes standard sets of both crash and capabilities data as described in Section 7. Entities along the path between the vehicle and the PSAP are able to identify the call as an ACN call and handle it appropriately. The PSAP is able to identify the crash and capabilities data included in the SIP INVITE request by examining the Call-Info header fields for "purpose" parameters whose values start with EmergencyCallData. The PSAP is able to access the data it is capable of handling and is interested in by checking the "purpose" parameter values. This document extends [RFC8147] by reusing the call setup and other normative requirements with the exception that in this document, support for the eCall MSD is OPTIONAL and support for VEDS is REQUIRED. This document also adds new attribute values to the metadata/control object defined in [RFC8147].
9. New Metadata/Control Values
This document adds new attribute values to the metadata/control structure defined in [RFC8147]. In addition to the base usage from the PSAP to the IVS to acknowledge receipt of crash data, the <ack> element is also contained in a metadata/control block sent by the IVS to the PSAP. This is used by the IVS to acknowledge receipt of a request by the PSAP and indicate if the request was carried out when that request would not otherwise be acknowledged (if the PSAP requests the vehicle to send data and the vehicle does so, the data serves as a success acknowledgment); see Section 8 for details. The <capabilities> element is used in a metadata/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 and all available lamps (lights) and cameras. New request values are added to the <request> element to enable the PSAP to request the vehicle to perform additional actions. Mandatory Actions (the IVS and the PSAP MUST support): o Transmit data object (VEDS MUST be supported; MSD MAY be supported) Optional Actions (the IVS and the PSAP MAY support): o Display and/or play static (pre-defined) message o Display and/or speak dynamic text (text supplied in action) o Flash or turn on or off a lamp (light) o Honk horn o Lock or unlock doors o Enable a camera The <ack> element indicates the object being acknowledged (i.e., a data object or a metadata/control block containing <request> elements) and reports success or failure. The <capabilities> element has child <request> elements indicating the actions (including data types, lamps (lights), and cameras) supported by the IVS. The <request> element contains attributes to indicate the request and to supply any needed information, and it MAY contain a <text> child element to contain the text for a dynamic message. The "action"
attribute is mandatory and indicates the specific action. [RFC8147] established an IANA registry to contain the allowed values; this document adds new values to that registry in Table 1.9.1. New Values for the "action" Attribute
The following new "action" values are defined: msg-static: displays or plays a pre-defined message (translated as appropriate for the language of the vehicle's interface). A registry is created in Section 14.4 for messages and their IDs. Vehicles include the highest registered message in their <capabilities> element to indicate support for all messages up to and including the indicated value. A registry of message identification values is defined in Section 14.4. There is only one static message initially defined (listed in Table 2). Because all compliant vehicles are expected to support all static messages translated into all languages supported by the vehicle, it is important to limit the number of such messages. Therefore, this registry operates under "Specification Required" rules as defined in [RFC5226], which requires a stable, public document and implies expert review of the publication. msg-dynamic: displays or speaks (via text-to-speech) a message contained in a child <text> element within the request. honk: sounds the horn. lamp: flashes a lamp (light) or turns it on or off. The lamp is identified by a lamp ID token contained in an "element-id" attribute of the request. The desired state of the lamp is either "on", "off", or "flash" as indicated in a "requested-state" attribute. The duration of the lamp's requested state is specified in a "persistence" attribute. A registry of lamp identification values is defined in Section 14.5. The initial values (listed in Table 3) are head, interior, fog-front, fog-rear, brake, brake-center, position-front, position-rear, turn-left, turn-right, and hazard. enable-camera: adds a one-way media stream (established via SIP re-INVITE sent by the vehicle) to enable the PSAP call taker to view a feed from a camera. A registry of camera identification values is defined in Section 14.6. The initial values (listed in Table 4) are backup, left-rear, right-rear, forward, rear-wide, lane, interior, night-front, night-rear, night-left, and night- right.
door-lock: locks or unlocks all door locks. A "requested-state"
attribute contains either "locked" or "unlocked" to indicate if
the doors are to be locked or unlocked.
Note that there is no "request" action to play dynamic media (such as
an audio message). The PSAP can send a SIP re-INVITE to establish a
one-way media stream for this purpose.
9.2. Example <request> 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">
<request action="send-data" datatype="VEDS"/>
<request action="lamp" element-id="hazard"
requested-state="flash" persistence="PT1H"/>
<request action="msg-static" int-id="1"/>
<request action="msg-dynamic">
<text>Remain calm. Help is on the way.</text>
</request>
</EmergencyCallData.Control>
Figure 7: <request> Example
9.3. The <ack> Element
The <ack> element is transmitted by the PSAP to acknowledge
unsolicited data sent by the IVS and transmitted by the IVS to
acknowledge receipt of a <request> element other than a successfully
performed "send-data" request (e.g., a request to display a message
to the vehicle occupants is acknowledged, but a request to transmit
VEDS data is not, since the transmitted VEDS serves as
acknowledgment). An <ack> element sent by an IVS references the
unique ID of the metadata/control object containing the request(s),
and for each request being acknowledged, it indicates whether the
request was successfully performed, and if not, it indicates why not.
9.3.1. Examples 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 ref="1234567890@atlanta.example.com"> <actionResult action="msg-dynamic" success="true"/> <actionResult action="lamp" success="false" reason="unable" details="The requested lamp is inoperable"/> </ack> </EmergencyCallData.Control> Figure 8: Example <ack> from IVS to PSAP9.4. The <capabilities> Element
The <capabilities> element [RFC8147] is transmitted by the IVS to indicate its capabilities to the PSAP. The <capabilities> element contains a <request> child element per action supported by the vehicle. The vehicle MUST support sending the VEDS data object and so includes at a minimum a <request> child element with the "action" attribute set to "send-data" and the "supported-values" attribute containing all data blocks supported by the IVS, which MUST include "VEDS". All other actions are OPTIONAL. If the "msg-static" action is supported, a <request> child element with the "action" attribute set to "msg-static" is included, with the "int-id" attribute set to the highest supported static message supported by the vehicle. A registry is created in Section 14.4 to map "int-id" values to static text messages. By sending the highest supported static message number in its <capabilities> element, the vehicle indicates its support for all static messages in the registry up to and including that value. If the "lamp" action is supported, a <request> child element with the "action" attribute set to "lamp" is included, with the "supported- values" attribute set to all supported lamp IDs. A registry is created in Section 14.5 to contain lamp ID values. If the "enable-camera" action is supported, a <request> child element with the "action" attribute set to "enable-camera" is included, with the "supported-values" attribute set to all supported camera IDs. A registry is created in Section 14.6 to contain camera ID values.
9.4.1. Example <capabilities> 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"> <capabilities> <request action="send-data" supported-values="VEDS"/> <request action="lamp" supported-values="head;interior;fog-front; fog-rear;brake;position-front;position-rear; turn-left;turn-right;hazard"/> <request action="msg-static" int-id="3"/> <request action="msg-dynamic"/> <request action="honk"/> <request action="enable-camera" supported-values="backup; interior"/> <request action="door-lock"/> </capabilities> </EmergencyCallData.Control> Figure 9: <capabilities> Example
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